Touch screen sensor with low visibility conductors

ABSTRACT

A touch screen sensor with a conductive micropattern includes one or more features to obscure or reduce the visibility of the conductive micropattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/393,197, filed Feb. 26, 2009, now allowed, the disclosure of which isincorporated by reference herein in its entirety, which claims thebenefit of U.S. Provisional Application Nos.; 61/085,799, filed Aug. 1,2008, the disclosure of which is incorporated by reference herein in itsentirety; and 61/085,764, filed Aug. 1, 2008, the disclosure of which isincorporated by reference herein in its entirety.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Provisional Application Nos.61/032,269, filed Feb. 28, 2008, the disclosure of which is incorporatedby reference herein in its entirety; 61/032,273, filed Feb. 28, 2008,the disclosure of which is incorporated by reference herein in itsentirety; 61/085,496, filed Aug. 1, 2008, the disclosure of which isincorporated by reference herein in its entirety

BACKGROUND

Touch screen sensors detect the location of an object (e.g. a finger ora stylus) applied to the surface of a touch screen display or thelocation of an object positioned near the surface of a touch screendisplay. These sensors detect the location of the object along thesurface of the display, e.g. in the plane of a flat rectangular display.Examples of touch screen sensors include capacitive sensors, resistivesensors, and projected capacitive sensors. Such sensors includetransparent conductive elements that overlay the display. The elementsare combined with electronic components that use electrical signals toprobe the elements in order to determine the location of an object nearor in contact with the display.

In the field of touch screen sensors, there is a need to have improvedcontrol over the electrical properties of the transparent touch screensensors, without compromising optical quality or properties of thedisplay. A transparent conductive region of a typical touch screensensor includes a continuous coating of a transparent conducting oxide(TCO) such as indium tin oxide (ITO), the coating exhibiting electricalpotential gradients based on the location or locations of contact to avoltage source and the overall shape of the region. This fact leads to aconstraint on possible touch sensor designs and sensor performance, andnecessitates such measures as expensive signal processing electronics orplacement of additional electrodes to modify the electrical potentialgradients. Thus, there is a need for transparent conductive elementsthat offer control over electrical potential gradients that isindependent of the aforementioned factors.

BRIEF SUMMARY

A touch sensor or touch sensitive device having features to obscure orreduce the visibility of conductive micropattern elements.

In one embodiment, a touch-sensitive device is described, the touchsensitive device comprising a first visible light transparent substratehaving a touch-interface surface and a display-interface surface, thetouch-interface surface disposed toward touch input, and the displayinterface disposed toward the output of a display; a second visiblelight transparent substrate having a first surface and a second surfaceand also having a touch sensing area comprised of an electricallyconductive micropattern disposed on or in the second visible lighttransparent substrate, wherein the micropattern includes conductors withwidth between about 1 and 10 micrometers; wherein the first surface ofthe second visible light transparent substrate is disposed toward thedisplay-interface surface of the first visible light transparentsubstrate; and wherein the first visible light transparent substrateincludes a feature that reduces the visibility of the micropattern.

In another embodiment, a touch screen sensor is described, the touchscreen sensor comprising, within a touch sensing area, a electricallyconductive micropattern disposed on or in a visible light transparentsubstrate, wherein the micropattern includes conductive traces withwidth between about 1 and 10 micrometers; one or moremicropattern-obscuring features to reduce the visibility of themicropattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 illustrates a schematic diagram of a touch screen sensor 100;

FIG. 2 illustrates a perspective view of a conductive visible lighttransparent region lying within a touch screen sensing area;

FIG. 3 illustrates a process for creating microconductors using UV lasercuring of a conductive ink;

FIG. 4 illustrates a gravure printing process for creatingmicroconductors;

FIG. 5 illustrates a cross section view of microreplicated channelsfilled with conductive material;

FIG. 6 illustrates a finger capacitively coupling with microreplicatedchannels filled with conductive material;

FIG. 7 illustrates patterns of microconductors produced on a flexiblesubstrate, useful for producing touch sensors;

FIG. 8 illustrates parallel microconductors printed on a flexible webmaterial in the downweb direction;

FIG. 9 illustrates a section of the flexible material from FIG. 8 havingadditional interconnecting conductors added;

FIG. 10 illustrates a cross section of an example of a matrix touchsensor constructed from two layers of the materials from FIG. 9;

FIG. 11 illustrates the conductor micropattern for one embodiment of thetouch screen sensor;

FIG. 12 illustrates a portion of the conductor micropattern illustratedin FIG. 3, the portion including a conductive mesh with selective breaksfor modulating the local sheet resistance as well as a larger feature inthe form of a contact pad;

FIG. 13 illustrates a modulation in resistance along the horizontal meshbars given in FIG. 3, created by selective breaks in the contiguousmesh;

FIG. 14 is a circuit diagram that approximates the properties of theconductor micropattern illustrated in FIG. 3, where capacitive platesare separated by resistive elements;

FIG. 15 illustrates the conductor micropattern for one embodiment of thetouch screen sensor, the micropattern including regions labeled 15 a-15e with different sheet resistance created in part by selective breaks inthe electrically conductive micropattern mesh;

FIGS. 15 a-15 e each illustrate a portion of the varying conductormicropattern illustrated in FIG. 15;

FIG. 16 illustrates the distribution of resistance per unit length alongthe long axis of the wedge-shaped transparent conductive region havingregions 15 a and 15 b therein, as compared with the resistance per unitlength for a similarly shaped region comprising only a uniformtransparent conducting oxide, ITO;

FIG. 17 illustrates the arrangement of layers that are laminatedtogether to form one embodiment of the touch screen sensor, an X-Y gridtype projected capacitive touch screen sensor;

FIG. 18 illustrates the conductor micropattern for the X-layer or theY-layer of an embodiment of the touch screen sensor according to FIG.17;

FIG. 19 illustrates a portion of the conductor micropattern illustratedin FIG. 10, the portion including a visible light transparent conductivemesh contacting a larger feature in the form of a contact pad, as wellas electrically isolated conductor deposits in the space between themesh regions;

FIG. 20 illustrates the conductor micropattern for the X-layer or theY-layer of another embodiment of the touch screen sensor according toFIG. 9;

FIG. 21 illustrates a portion of the conductor micropattern given inFIG. 12, the portion including a visible light transparent conductivemesh contacting a larger feature in the form of a contact pad, as wellas electrically isolated conductor deposits in the space between themesh regions;

FIG. 22 illustrates the conductor micropattern for the X-layer or theY-layer of another embodiment of the touch screen sensor according toFIG. 17; and

FIG. 23 illustrates a portion of the conductor micropattern given inFIG. 22, the portion including a visible light transparent conductivemesh contacting a larger feature in the form of a contact pad, as wellas electrically isolated conductor deposits in the space between themesh regions.

FIG. 24 illustrates a graph to reflect optical quality of the touchscreen sensor, the graph being a plot of Percent of Open Area vs.conductor trace width (in micrometers), with Region 3 being good opticalquality that can be used for a touch screen sensor, Region 2 beingbetter in optical quality as compared to Region 2, and Region 1 havingthe best optical quality of the three regions. Percent of Open Area isused interchangeably with open area fraction herein.

FIG. 25 and FIG. 26 illustrate scanning electron photomicrographs of thegeometry for the hexagonal mesh (sometimes referred to as “hex” mesh)and square mesh that are characteristic of Examples 6 through 40. Thelight shade lines in each image represent the pattern of the metalconductor and the dark area represents the substrate used in theExamples.

FIGS. 27, 27 a, and 27 b illustrate various portions of a firstpatterned substrate;

FIGS. 28, 28 a, and 28 b illustrate various portions of a secondpatterned substrate;

FIG. 29 illustrates a projected capacitive touch screen transparentsensor element constructed from the first and second patternedsubstrates of FIGS. 27 and 28.

FIG. 30 illustrates a perspective view of a conductive visible lighttransparent region lying within a touch screen sensing area;

FIG. 31 illustrates a micropattern obscuring feature positioned betweena finger and a micropatterned microconductor.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying setof drawings that form a part hereof and in which are shown by way ofillustration several specific embodiments. It is to be understood thatother embodiments are contemplated and may be made without departingfrom the scope or spirit of the present invention. The followingdetailed description, therefore, is not to be taken in a limiting sense.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the context clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the context clearlydictates otherwise.

As used herein, “visible light transparent” refers to the level oftransmission being at least 60 percent transmissive to at least onepolarization state of visible light, where the percent transmission isnormalized to the intensity of the incident, optionally polarized light.It is within the meaning of visible light transparent for an articlethat transmits at least 60 percent of incident light to includemicroscopic features (e.g., dots, squares, or lines with minimumdimension, e.g. width, between 0.5 and 10 micrometers, or between 1 and5 micrometers) that block light locally to less than 80 percenttransmission (e.g., 0 percent); however, in such cases, for anapproximately equiaxed area including the microscopic feature andmeasuring 1000 times the minimum dimension of the microscopic feature inwidth, the average transmittance is greater than 60 percent.

The present disclosure relates to touch screen sensors with electricaland optical properties that are engineered through design of conductormicropatterns comprised therein. There are several advantages that arecreated for touch screen sensors by the incorporation of the conductormicropatterns described herein. In some embodiments, the transparentconductive properties within a transparent conductive region areengineered to control the electrical potential gradient within the touchsensing region during use. This leads to simplicity of signal processingelectronics and, for some touch screen sensor types simplicity in thedesign of (or elimination of the need for) additional conductor patternsthat would otherwise be needed for electrical potential gradient(electrical field) linearization. In some embodiments, the electricalproperties of the touch screen sensors described herein are designed togenerate a controlled electrical potential gradient along a transparentsensor element. E.g., the electrical properties are designed to create alinear electrical potential gradient along a particular direction withina transparent conductive region, the overall shape of which wouldordinarily lead to a non-linear gradient if a standard transparentconductor material was used (e.g., continuous ITO coating). In someembodiments, the electrical properties are designed to create a level ofnon-linearity of electrical potential gradient for a transparentconductive region that is greater than that which would be presentwithin a transparent conductive region of the same shape but comprisedof a standard transparent conductor material (e.g., continuous ITOcoating). In more detail, for a rectangular capacitive touch screencomprising a contiguous transparent sheet conductor in the form of amicropatterned conductor with electrical connections made to the cornersof the sensing area, the linearity of electrical potential gradient (anduniformity of electric field) across the sensing area in the verticaland horizontal directions can be improved by engineering the areadistribution of sheet resistance values and anisotropy in such a way asto distribute the field more uniformly. In other embodiments, the sensorincludes conductor elements comprised of the same conductor material atthe same thickness (i.e., height), but with different effective sheetresistance by virtue of micropatterning. E.g., in some embodiments, thesame conductor material at the same thickness (i.e., height) is used togenerate conductive traces that define a first micropattern geometry,leading to a first level of sheet resistance in a transparent conductiveregion, and conductive traces that define a second micropatterngeometry, leading to a second level of sheet resistance in a secondtransparent conductive region. This disclosure also allows for improvedefficiency and resource utilization in the manufacture of transparentdisplay sensors, e.g. through the avoidance of rare elements such asindium for some embodiments, e.g. embodiments based on micropatternedmetal conductors.

The disclosure further relates to contact or proximity sensors for touchinput of information or instructions into electronic devices (e.g.,computers, cellular telephones, etc.) These sensors are visible lighttransparent and useful in direct combination with a display, overlayinga display element, and interfaced with a device that drives the display(as a “touch screen” sensor). The sensor element has a sheet like formand includes at least one electrically insulating visible lighttransparent substrate layer that supports one or more of the following:i) conductive material (e.g., metal) that is mesh patterned onto twodifferent regions of the substrate surface with two different meshdesigns so as to generate two regions with different effective sheetresistance values, where at least one of the regions is a transparentconductive region that lies within the touch-sensing area of the sensor;ii) conductive material (e.g., metal) that is patterned onto the surfaceof the substrate in a mesh geometry so as to generate a transparentconductive region that lies within the touch sensing area of the sensorand that exhibits anisotropic effective sheet resistance; and/or iii)conductive material (e.g., metal) that is patterned onto the surface ofthe substrate in a mesh geometry within an effectively electricallycontinuous transparent conductive region, the geometry varying withinthe region so as to generate different values of local effective sheetresistance in at least one direction (e.g., continuously varying sheetresistance for the transparent conductive region), where the region lieswithin the sensing area of the touch sensor.

The sensing area of a touch sensor is that region of the sensor that isintended to overlay, or that overlays, a viewable portion of aninformation display and is visible light transparent in order to allowviewability of the information display. Viewable portion of theinformation display refers to that portion of an information displaythat has changeable information content, e.g. the portion of a display“screen” that is occupied by pixels, e.g. the pixels of a liquid crystaldisplay.

This disclosure further relates to touch screen sensors that are of theresistive, capacitive, and projected capacitive types. The visible lighttransparent conductor micropatterns are particularly useful forprojected capacitive touch screen sensors that are integrated withelectronic displays. As a component of projected capacitive touch screensensors, the visible light transparent conductive micropattern areuseful for enabling high touch sensitivity, multi-touch detection, andstylus input.

The two or more different levels of sheet resistance, the anisotropy ofthe sheet resistance, or the varying level of sheet resistance within atransparent conductive region can be controlled by the geometries oftwo-dimensional meshes that make up the transparent micropatternedconductors, as described below.

While the present invention is not so limited, an appreciation ofvarious aspects of the invention will be gained through a discussion ofthe examples provided below.

FIG. 1 illustrates a schematic diagram of a touch screen sensor 100. Thetouch screen sensor 100 includes a touch screen panel 110 having a touchsensing area 105. The touch sensing area 105 is electrically coupled toa touch sensor drive device 120. The touch screen panel 110 isincorporated into a display device.

FIG. 2 illustrates a perspective view of a conductive visible lighttransparent region 101 that would lie within a touch sensing area of atouch screen panel, e.g., touch sensing area 105 in FIG. 1. Theconductive visible light transparent region 101 includes a visible lighttransparent substrate 130 and an electrically conductive micropattern140 disposed on or in the visible light transparent substrate 130. Thevisible light transparent substrate 130 includes a major surface 132 andis electrically insulating. The visible light transparent substrate 130can be formed of any useful electrically insulating material such as,e.g., glass or polymer. Examples of useful polymers for lighttransparent substrate 130 include polyethylene terephthalate (PET) andpolyethylene naphthalate (PEN). The electrically conductive micropattern140 can be formed of a plurality of linear metallic features.

FIG. 2 also illustrates an axis system for use in describing theconductive visible light transparent region 101 that would lie within atouch sensing area of a touch screen panel. Generally, for displaydevices, the x and y axes correspond to the width and length of thedisplay and the z axis is typically along the thickness (i.e., height)direction of a display. This convention will be used throughout, unlessotherwise stated. In the axis system of FIG. 2, the x axis and y axisare defined to be parallel to a major surface 132 of the visible lighttransparent substrate 130 and may correspond to width and lengthdirections of a square or rectangular surface. The z axis isperpendicular to that major surface and is typically along the thicknessdirection of the visible light transparent substrate 130. A width of theplurality of linear metallic features that form the electricallyconductive micropattern 140 correspond to an x-direction distance forthe parallel linear metallic features that extend linearly along the yaxis and a y-direction distance for the orthogonal linear metallicfeatures correspond to a width of the orthogonal linear metallicfeatures. A thickness or height of the linear metallic featurescorresponds to a z-direction distance.

In some embodiments, the conductive visible light transparent region 101that would lie within a touch sensing area of a touch screen panelincludes two or more layers of visible light transparent substrate 130each having a conductive micropattern 140.

The conductive micropattern 140 is deposited on the major surface 132.Because the sensor is to be interfaced with a display to form a touchscreen display, or touch panel display, the substrate 130 is visiblelight transparent and substantially planar. The substrate and the sensormay be substantially planar and flexible. By visible light transparent,what is meant is that information (e.g., text, images, or figures) thatis rendered by the display can be viewed through the touch sensor. Theviewability and transparency can be achieved for touch sensors includingconductors in the form of a deposited metal, even metal that isdeposited with thickness great enough to block light, if the metal isdeposited in an appropriate micropattern.

The conductive micropattern 140 includes at least one visible lighttransparent conductive region overlaying a viewable portion of thedisplay that renders information. By visible light transparentconductive, what is meant is that the portion of the display can beviewed through the region of conductive micropattern and that the regionof micropattern is electrically conductive in the plane of the pattern,or stated differently, along the major surface of the substrate ontowhich the conductive micropattern is deposited and to which it isadjacent. Preferred conductive micropatterns include regions with twodimensional meshes, e.g. square grids, rectangular (non-square) grids,or regular hexagonal networks, where conductive traces define enclosedopen areas within the mesh that are not deposited with conductor that isin electrical contact with the traces of the mesh. The open spaces andassociated conductor traces at their edges are referred to herein ascells. Other useful geometries for mesh cells include random cell shapesand irregular polygons.

In some embodiments, the conductive traces defining the conductivemicropattern are designed not to include segments that are approximatelystraight for a distance greater than the combined edge length of fiveadjacent cells, preferably four adjacent cells, more preferably threeadjacent cells, even more preferably two adjacent cells. Mostpreferably, the traces defining the micropattern are designed not toinclude segments that are straight for a distance greater than the edgelength of a single cell. Accordingly, in some embodiments, the tracesthat define the micropattern are not straight over long distances, e.g.,10 centimeters, 1 centimeter, or even 1 millimeter. Patterns withminimal lengths of straight line segments, as just described, areparticularly useful for touch screen sensors with the advantage ofcausing minimal disturbance of display viewability.

The two-dimensional geometry of the conductive micropattern (that is,geometry of the pattern in the plane or along the major surface of thesubstrate) can be designed, with consideration of the optical andelectrical properties of the conductor material, to achieve specialtransparent conductive properties that are useful in touch screensensors. E.g., whereas a continuous (un-patterned) deposit or coating ofconductor material has a sheet resistance that is calculated as its bulkresistivity divided by its thickness, in the present invention differentlevels of sheet resistance are engineered by micropatterning theconductor as well.

In some embodiments, the two-dimensional conductive micropattern isdesigned to achieve anisotropic sheet resistance in a conductive region(e.g., a visible light transparent conductive region) of the sensor. Byanisotropic sheet resistance, what is meant is that the magnitude of thesheet resistance of the conductive micropattern is different whenmeasured or modeled along two orthogonal directions.

In contrast, in some embodiments, the two-dimensional conductivemicropattern is designed to achieve isotropic sheet resistance in aconductive region (e.g., a visible light transparent conductive region)of the sensor. By isotropic sheet resistance, what is meant is that themagnitude of the sheet resistance of the conductive micropattern is thesame when measured or modeled along any two orthogonal directions in theplane, as in the case for a square grid formed with traces of constantwidth for both directions.

Anisotropic sheet resistance within a region can include sheetresistance in one direction that is at least 10 percent greater than thesheet resistance in the orthogonal direction, or at least 25 percentgreater, at least 50 percent greater, at least 100 percent greater, atleast 200 percent greater, at least 500 percent greater, or even atleast 10 times greater. In some embodiments, anisotropic sheetresistance within a region includes sheet resistance in one directionthat is greater than the sheet resistance in the orthogonal direction bya factor of at least 1.5. In some embodiments, anisotropic sheetresistance within a region includes sheet resistance in one directionthat is greater than the sheet resistance in the orthogonal direction bya factor between 1.1 and 10, in other embodiments between 1.25 and 5,and in yet other embodiments between 1.5 and 2.

An example of a conductive micropattern geometry that can generateanisotropic sheet resistance is approximately a rectangular microgrid(non-square) with fixed widths for the conductive traces. For such arectangular microgrid (non-square), anisotropic sheet resistance canresult from a repeating geometry for the cells of the grid that includesone edge that is 10 percent longer than the other, 25 percent longerthan the other, at least 50 percent longer than the other, 100 percentlonger than the other, or even 10 times longer than the other.Anisotropic sheet resistance can be created by varying the width oftraces for different directions, e.g. in an otherwise highly symmetricalpattern of cells for a mesh. An example of the latter approach togenerating anisotropic sheet resistance is a square grid of conductivetraces, e.g. with pitch of 200 micrometers, wherein the traces in afirst direction are 10 micrometers wide and the traces in the orthogonaldirection are 9 micrometers in width, 7.5 micrometers in width, 5micrometers in width, or even 1 micrometer in width. Anisotropic sheetresistance within a region can include a finite, measurable sheetresistance in one direction and essentially infinite sheet resistance inthe other direction, as would be generated by a pattern of parallelconductive lines. In some embodiments, as described above, theanisotropic sheet resistance within a region includes a finite,measurable sheet resistance in a first direction and a finite,measurable sheet resistance in the direction orthogonal to the firstdirection.

For the purpose of determining whether a region of conductivemicropattern is isotropic or anisotropic, it will be appreciated bythose skilled in the art that the scale of the region of interest mustbe reasonably selected, relative to the scale of the micropattern, tomake relevant measurements or calculations of properties. E.g., once aconductor is patterned at all, it is trivial for one to select alocation and a scale on which to make a measurement that will yield adifference in sheet resistance for different directions of measurement.The following detailed example can make the point more clearly. If oneconsidered a conductor pattern of isotropic geometry in the form of asquare grid with 100 micrometer wide conductor traces and 1 millimeterpitch (leading to 900 micrometer by 900 micrometer square openings inthe grid), and one made four point probe measurements of sheetresistance within one of the traces along the edge of a square openingwith a probe having fixed spacing along the four linearly arrangedprobes of 25 micrometers (leading to a separation between the twocurrent probes, the outside probes, of 75 micrometers), different levelsof sheet resistance will be calculated by the measured values of currentand voltage depending on whether the probes were aligned parallel to thetrace or orthogonal to the trace. Thus, even though the square gridgeometry would yield isotropic sheet resistance on a scale larger thanthe square grid cell size, it is possible for one to carry outmeasurements of sheet resistance that would suggest anisotropy. Thus,for the purpose of defining anisotropy of the sheet resistance of aconductive micropattern in the current disclosure, e.g. a visible lighttransparent conductive region of the micropattern that comprises a mesh,the relevant scale over which the sheet resistance should be measured ormodeled is greater than the length scale of a cell in the mesh,preferably greater than the length scale of two cells. In some cases,the sheet resistance is measured or modeled over the length scale offive or more cells in the mesh, to show that the mesh is anisotropic inits sheet resistance.

In contrast to embodiments where the conductive micropattern exhibitsanisotropy of sheet resistance in a region, sensors includingtransparent conducting oxide thin films (e.g., indium tin oxide, or ITO)exhibit isotropic sheet resistance in contiguous regions of theconductor. In the latter case, one can measure or model that asfour-point probe measurements of sheet resistance of a contiguous regionare made in different directions and with decreasing spacing between theprobes, the same readings of current and voltage for differentdirections clearly indicate isotropy.

In some embodiments, the two-dimensional conductive micropattern isdesigned to achieve different levels, or magnitudes, of sheet resistancein two different patterned conductor regions of the sensor, whenmeasured in a given direction. E.g., with respect to the differentlevels of sheet resistance, the greater of the two may exceed the lesserby a factor greater than 1.25, a factor greater than 1.5, a factorgreater than 2, a factor greater than 5, a factor greater than 10, oreven a factor greater than 100. In some embodiments, the greater of thetwo sheet resistance values exceeds the lesser by a factor between 1.25and 1000, in other embodiments between 1.25 and 100, in otherembodiments between 1.25 and 10, in other embodiments between 2 and 5.For a region to be regarded as having a different sheet resistance fromthat of another region, it would have a sheet resistance that is greateror lesser than that of the other region by a factor of at least 1.1.

In some embodiments, the micropattern is designed to achieve theaforementioned different levels of sheet resistance for two patternedconductor regions that are electrically contiguous, which is to say thatthey are patterned conductor regions that are in electrical contact witheach other along a boundary between them. Each of the two patternedconductor regions that share a conductive boundary may have uniformrespective pattern geometries, but again different. In some embodiments,the micropattern is designed to achieve the different levels of sheetresistance for two different patterned conductor regions that areelectrically noncontiguous, which is to say that the they are patternedconductor regions that share no boundary between them for which thepatterned regions are in electrical contact along that boundary. Each ofthe two patterned conductor regions that share no conductive boundarybetween them may have uniform respective pattern geometries, but againdifferent. For electrically noncontiguous regions, it is within thescope of the disclosure for them both to make electrical contact in thepattern to the same solid conductor element, e.g. a bus bar or pad. Insome embodiments, the micropattern is designed to achieve the differentlevels of sheet resistance for two regions that are electricallyisolated from each other and thus can be addressed independently byelectrical signals. Each of the two mesh regions that are electricallyisolated may have a uniform pattern geometry, but again different.Finally, in some embodiments, the micropattern is designed to achievedifferent levels of sheet resistance for two different regions bycreating continuously varying sheet resistance from the first region tothe second, and example of two regions that are electrically contiguous.

The two dimensional conductive micropatterns that include two regionswith different sheet resistance in a measurement direction are usefulfor designing a visible light transparent conductive region in thesensing area with a preferred level of sheet resistance for that region(e.g., low sheet resistance between 5 and 100 ohms per square),including varying or anisotropic sheet resistance optionally, anddesigning an electrical element, e.g. a resistor element, as part of thetouch screen sensor that may or may not lie within the sensing area, theresistor element comprising a sheet conductor with sheet resistanceselected optimally for the resistor function (e.g., higher sheetresistance between 150 and 1000 ohms per square) and possibly in lightof other design constraints, e.g. the constraint of minimizing thefootprint of the resistor.

The sheet resistance of the conductive micropattern, in regions anddirections with finite sheet resistance that can be measured or modeled,as described above, may fall within the range of 0.01 ohms per square to1 megaohm per square, or within the range of 0.1 to 1000 ohms persquare, or within the range of 1 to 500 ohms per square. In someembodiments, the sheet resistance of the conductive micropattern fallswithin the range of 1 to 50 ohms per square. In other embodiments, thesheet resistance of the conductive micropattern falls within the rangeof 5 to 500 ohms per square. In other embodiments, the sheet resistanceof the conductive micropattern falls within the range of 5 to 100 ohmsper square. In other embodiments, the sheet resistance of the conductivemicropattern falls within the range of 5 to 40 ohms per square. In otherembodiments, the sheet resistance of the conductive micropattern fallswithin the range of 10 to 30 ohms per square. In prescribing the sheetresistance that may characterize a conductive micropattern or a regionof a conductive micropattern, the micropattern or region of micropatternis said to have a sheet resistance of a given value if it has that sheetresistance value for electrical conduction in any direction.

Appropriate micropatterns of conductor for achieving transparency of thesensor and viewability of a display through the sensor have certainattributes. First of all, regions of the conductive micropattern throughwhich the display is to be viewed should have an area fraction of thesensor that is shadowed by the conductor of less than 50%, or less than25%, or less than 20%, or less than 10%, or less than 5%, or less than4%, or less than 3%, or less than 2%, or less than 1%, or in a rangefrom 0.25 to 0.75%, or less than 0.5%.

The open area fraction (or open area or Percentage of Open Area) of aconductive micropattern, or region of a conductive micropattern, is theproportion of the micropattern area or region area that is not shadowedby the conductor. The open area is equal to one minus the area fractionthat is shadowed by the conductor, and may be expressed conveniently,and interchangeably, as a decimal or a percentage. Area fraction that isshadowed by conductor is used interchangeably with the density of linesfor a micropatterned conductor. Micropatterned conductor is usedinterchangeably with electrically conductive micropattern and conductivemicropattern. Thus, for the values given in the above paragraph for thefraction shadowed by conductor, the open area values are greater than50%, greater than 75%, greater than 80%, greater than 90%, greater than95%, greater than 96%, greater than 97%, greater than 98%, greater than99%, 99.25 to 99.75%, 99.8%, 99.85%, 99.9% and even 99.95. In someembodiments, the open area of a region of the conductor micropattern(e.g., a visible light transparent conductive region) is between 80% and99.5%, in other embodiments between 90% and 99.5%, in other embodimentsbetween 95% and 99%, in other embodiments between 96% and 99.5%, inother embodiments between 97% and 98%, and in other embodiments up to99.95%. With respect to the reproducible achievement of useful opticalproperties (e.g. high transmission and invisibility of conductivepattern elements) and electrical properties, using practicalmanufacturing methods, preferred values of open area are between 90 and99.5%, more preferably between 95 and 99.5%, most preferably between 95and 99.95%.

To minimize interference with the pixel pattern of the display and toavoid viewability of the pattern elements (e.g., conductor lines) by thenaked eye of a user or viewer, the minimum dimension of the conductivepattern elements (e.g., the width of a line or conductive trace) shouldbe less than or equal to approximately 50 micrometers, or less than orequal to approximately 25 micrometers, or less than or equal toapproximately 10 micrometers, or less than or equal to approximately 5micrometers, or less than or equal to approximately 4 micrometers, orless than or equal to approximately 3 micrometers, or less than or equalto approximately 2 micrometers, or less than or equal to approximately 1micrometer, or less than or equal to approximately 0.5 micrometer.

In some embodiments, the minimum dimension of conductive patternelements is between 0.5 and 50 micrometers, in other embodiments between0.5 and 25 micrometers, in other embodiments between 1 and 10micrometers, in other embodiments between 1 and 5 micrometers, in otherembodiments between 1 and 4 micrometers, in other embodiments between 1and 3 micrometers, in other embodiments between 0.5 and 3 micrometers,and in other embodiments between 0.5 and 2 micrometers. With respect tothe reproducible achievement of useful optical properties (e.g. hightransmission and invisibility of conductive pattern elements with thenaked eye) and electrical properties, and in light of the constraint ofusing practical manufacturing methods, preferred values of minimumdimension of conductive pattern elements are between 0.5 and 5micrometers, more preferably between 1 and 4 micrometers, and mostpreferably between 1 and 3 micrometers.

In general, the deposited electrically conductive material reduces thelight transmission of the touch sensor, undesirably. Basically, whereverthere is electrically conductive material deposited, the display isshadowed in terms of its viewability by a user. The degree ofattenuation caused by the conductor material is proportional to the areafraction of the sensor or region of the sensor that is covered byconductor, within the conductor micropattern.

In general, it is desirable for a transparent touch screen sensor toexhibit a low value of haze. Haze refers to a property related to thescattering of light as it passes through a medium, e.g. as measured by aHaze-Gard instrument (Haze-Gard plus, BYK Gardner, Columbia, Md.). Insome embodiments, the touch screen sensor exhibits haze less than 10%,in some embodiments less than 5%, in some embodiments less than 4%, insome embodiments less than 3%, in some embodiments less than 2%.Embodiments are disclosed which achieve a desirable combination of hightransmission (also referred to as visible light transmittance), lowhaze, and low conductor trace visibility for regions including conductormicropatterns. The conductor micropatterns are thus especially usefulwhen used as part of a sensing area or region of a touch screen sensordisplay, e.g. when the micropattern overlays a viewable region of thedisplay.

In some embodiments, in order to generate a visible light transparentdisplay sensor that has uniform light transmission across the viewabledisplay field, even if there is a non-uniform distribution of sheetresistance, e.g. derived from a non-uniform mesh of conductive material,the sensors include isolated conductor deposits added to the conductormicropattern that serve to maintain the uniformity of lighttransmittance across the pattern. Such isolated conductor deposits arenot connected to the drive device (e.g., electrical circuit or computer)for the sensor and thus do not serve an electrical function. Forexample., a metal conductor micropattern that includes a first regionwith a mesh of square grid geometry of 3 micrometer line width and 200micrometer pitch (3% of the area is shadowed by the metal, i.e., 97%open area) and second region with a mesh of square grid geometry of 3micrometer line width and 300 micrometer pitch (2% of the area isshadowed by the metal, i.e., 98% open area) can be made opticallyuniform in its average light transmission across the two regions byincluding within each of the open cells of the 300 micrometer pitch gridregion one hundred evenly spaced 3 micrometer by 3 micrometer squares ofmetal conductor in the pattern. The one hundred 3 micrometer by 3micrometer squares (900 square micrometers) shadow an additional 1percent of the area for each 300 micrometer by 300 micrometer cell(90000 square micrometers), thus making the average light transmissionof the second region equal to that of the first region. Similar isolatedmetal features can be added in regions of space between contiguoustransparent conductive regions, e.g. contiguous transparent conductiveregions that include micropatterned conductors in the form of twodimensional meshes or networks, in order to maintain uniformity of lighttransmittance across the sensor, including the transparent conductiveregions and the region of space between them. In addition to isolatedsquares of conductor, other useful isolated deposits of conductor fortailoring optical uniformity include circles and lines. The minimumdimension of the electrically isolated deposits (e.g., the edge lengthof a square feature, the diameter of a circular feature, or the width ofa linear feature) is less than 10 micrometers, less than 5 micrometers,less than 2 micrometers, or even less than 1 micrometer.

With respect to the reproducible achievement of useful opticalproperties (e.g. high transmission and invisibility of conductivepattern elements), using practical manufacturing methods, the minimumdimension of the electrically isolated deposits is preferably between0.5 and 10 micrometers, more preferably between 0.5 and 5 micrometers,even more preferably between 0.5 and 4 micrometers, even more preferablybetween 1 and 4 micrometers, and most preferably between 1 and 3micrometers. In some embodiments, the arrangement of electricallyisolated conductor deposits is designed to lack periodicity. A lack ofperiodicity is preferred for limiting unfavorable visible interactionswith the periodic pixel pattern of an underlying display. For anensemble of electrically isolated conductor deposits to lackperiodicity, there need only be a single disruption to the otherwiseperiodic placement of at least a portion of the deposits, across aregion having the deposits and lacking micropattern elements that areconnected to decoding or signal generation and/or processingelectronics. Such electrically isolated conductor deposits are said tohave an aperiodic arrangement, or are said to be an aperiodicarrangement of electrically isolated conductor deposits. In someembodiments, the electrically isolated conductor deposits are designedto lack straight, parallel edges spaced closer than 10 micrometersapart, e.g. as would exist for opposing faces of a square deposit withedge length of 5 micrometers. More preferably the isolated conductordeposits are designed to lack straight, parallel edges spaced closerthan 5 micrometers apart, more preferably 4 micrometers apart, even morepreferably 3 micrometers apart, even more preferably 2 micrometersapart. Examples of electrically isolated conductor deposits that lackstraight, parallel edges are ellipses, circles, pentagons, heptagons,and triangles. The absence within the design of electrically isolatedconductor deposits of straight, parallel edges serves to minimizelight-diffractive artifacts that could disrupt the viewability of adisplay that integrates the sensor.

The impact of the conductor micropattern on optical uniformity can bequantified. If the total area of the sensor, and hence the conductormicropattern, that overlays a viewable region of the display issegmented into an array of 1 millimeter by 1 millimeter regions,preferred sensors include conductor micropatterns wherein none of theregions have a shadowed area fraction that differs by greater than 75percent from the average for all of the regions. More preferably, nonehave a shadowed area fraction that differs by greater than 50 percent.More preferably, none have a shadowed area fraction that differs bygreater than 25 percent. Even more preferably, none have a shadowed areafraction that differs by greater than 10 percent. If the total area ofthe sensor, and hence the conductor micropattern, that overlays aviewable region of the display is segmented into an array of 5millimeter by 5 millimeter regions, preferred sensors include conductormicropatterns wherein none of the regions have a shadowed area fractionthat differs by greater than 50 percent from the average for all of theregions. Preferably, none have a shadowed area fraction that differs bygreater than 50 percent. More preferably, none have a shadowed areafraction that differs by greater than 25 percent. Even more preferably,none have a shadowed area fraction that differs by greater than 10percent.

The disclosure advantageously allows for the use of metals as theconductive material in a transparent conductive sensor, as opposed totransparent conducting oxides (TCO's), such as ITO. ITO has certaindrawbacks, such as corrosion-related degradation in certainconstructions, a tendency to crack when flexed, high attenuation oftransmitted light (due to reflection and absorption) when deposited as acoating with sheet resistance below 100 to 1000 ohms per square, andincreasing cost due to the scarcity of indium. ITO is also difficult todeposit with uniform and reproducible electrical properties, leading tothe need for more complex and expensive electronics that couple to theconductive pattern to construct a touch screen sensor.

Examples of useful metals for forming the electrically conductivemicropattern include gold, silver, palladium, platinum, aluminum,copper, nickel, tin, alloys, and combinations thereof. In someembodiments, the conductor is a transparent conducting oxide. In someembodiments the conductor is ITO. The conductor may have a thicknessbetween 5 nanometers and 5 micrometers, or between 10 nanometers and 500nanometers, or between 15 nanometers and 250 nanometers. In manyembodiments, the thickness of the conductor is less than one micrometer.A desired thickness for the conductor can be calculated by starting withthe desired sheet resistance and considering the micropattern geometry(and in turn its effect on the current-carrying cross-section in theplane) and the bulk resistivity of the conductor, as is known in theart. For complicated geometries of micropattern, there are computationalmethods in the art, e.g. finite difference methods or finite elementmethods that can be used to calculate sheet resistance, referred toherein as modeling the properties of a micropattern. Sheet resistancecan be measured using a number of techniques, including four-point probetechniques and non-contact eddy-current methods, as are known in theart.

Examples of useful displays with which sensors of the invention can beintegrated include liquid crystal displays, cathode ray tube displays,plasma display panels, and organic light emitting diode displays.

Conductor patterns according to the invention can be generated by anyappropriate patterning method, e.g. methods that includephotolithography with etching or photolithography with plating (see,e.g., U.S. Pat. No. 5,126,007; U.S. Pat. No. 5,492,611; U.S. Pat. No.6,775,907). Additionally, the conductor patterns can be createdutilizing one of several other exemplary methods (each discussed in moredetail below):

-   -   1. Laser cured masking (curing of a mask layer on a metal film,        and then etching);    -   2. Inkjet printing (of masking material or of seed material for        subsequent metal plating);    -   3. Gravure printing (of a seed material for subsequent metal        plating);    -   4. Micro-replication (form micro-grooves in a substrate, then        fill with conductive material or with a seed material for        subsequent metal plating); or,    -   5. Micro-contact printing (stamping or rotary printing of        self-assembled monolayer (SAM) patterns on a substrate's        surface).

Utilizing high volume, high resolution printing methods generally allowfor precision placement of the conductive elements, and also allows forthe (pseudo-random) variation of the microconductors at a scalecompatible with commercially available display pixels, to limit opticalanomalies (for example moiré patterns) that might otherwise occur.

Certain embodiments discussed herein may employ flat-sided “wire-like”conductors that enable greater light transmission than existing sensorsthat utilize transparent conductors. These flat-sided “wire-like”conductors, in some embodiments, provide greater scalability and controlof conductor placement than is possible with existing round wiresolutions. Micro-conductors discussed herein include conductors withmaximum cross sectional dimension of 10 micrometers or less. Less than 3micrometers is preferred for many sensor applications. Methods ofutilizing masking and etching typically produce a low-aspect (0.05 to0.5 μm thick×1 μm to 10 μm wide) microconductor. Micro-replicatedgrooves can produce higher aspect ratio microconductors, up to greaterthan 1:1.

Laser cured masking can be used to create microconductors by selectivelycuring a pattern with an ultraviolet laser. Such a process typicallyworks with either film—(for example, PET) or glass-based substrates. Anexemplary laser cured masking process may include the following steps:

-   -   1. A substrate is plated with metal, (for example, silver or        copper is sputter coated onto glass or PET film);    -   2. UV curable masking ink is coated uniformly onto the plated        substrate, (for example, spin coating, and dip coating);    -   3. A laser cures a portion of the printed ink, to form        microconductor electrodes in the active area of the touch        sensor, and may also cure (wider) lines that interconnect        electrodes to connector pads (beam width of the laser may be        reduced by a photo mask);    -   4. Uncured ink is removed (washed off); and    -   5. Metal plated on the substrate is removed by etching, except        for the pattern under the masking ink.

Inkjet Printing and plating of seed ink can be used to createmicroconductors by printing of the desired pattern using relatively widelines of seed ink (catalytic ink), followed by selective curing with aUV laser, and similar to the laser cured masking process describedabove. The substrate for this process may be either film—(for example,PET) or glass.

FIG. 3 a and FIG. 3 b show such a process, whereby:

-   -   1. Seed ink 66 is inkjet printed onto a substrate 67;    -   2. A laser 65 cures a portion of the printed ink, to form        microconductor electrodes 68 in active area(s) of the touch        sensor, and may also cure (wider) lines that interconnect        electrodes to connector pads (the beam width of the laser may be        reduced by a photo mask);    -   3. Uncured ink is removed (washed off); and,    -   4. The cured pattern of seed ink is electroless plated, (with a        conductive metal).        The inkjet printing process minimizes the amount of ink used, so        it should be considered where inks are expensive, (for example,        seed inks) If ink has relatively low cost, inkjet printing can        be replaced by another process (for example, spin coating or dip        coating) that coats the whole substrate uniformly. Ink material        and processing for the Inkjet printing and plating of seed ink        process described above are available from Conductive Inkjet        Technology division of Carclo Technical Plastics, Cambridge, UK.

Gravure printing requires that the image to be printed is “etched” intoa metal plate which rotates on a drum. As the drum turns, the etchedsurface is filled with ink which then gets deposited on the surface ofthe film being printed as the ink-filled etched plate and the filmcontact each other. The process is diagramed in FIG. 4, which shows afilm substrate 76 being printed with ink lines 74 from ink bath 73.Impression cylinder 70 is rolls against printing drum 75, which hasetches 72 that fill with ink from inkbath 73. Such a process could beused to make stock material for later processing or could be used tomake specific X or Y components of a high volume sensor.

Seed inks (or catalytic inks) may be printed by any of the methodsdescribed above. After printing and curing, the inks can be electrolessplated with metals such as copper, resulting in high conductivity. Seedink manufacturers include Conductive Inkjet Technology, a division ofCarclo, located in Cambridge, UK and QinetiQ Company in Farnborough,England. Cabot Printable Electronics and Displays of Albuquerque, N.Mex. make inkjet printable silver conductive inks.

Micro-replication is yet another process that can be used to formmicrocondcutors. The diagram in FIG. 5 shows a cross sectional view offilled, or partially filled, micro-replicated channels. The channels maybe filled with seed ink 81 and then plated (see metallization layer 80)to make them conductive. Alternatively the channels could be filled withan ink that by itself is conductive, eliminating the need for theplating process. A third alternative is to coat the substrate with ametal, then mask the portions of metal in the (bottom of) the grooves,then etch away the unmasked metal, (see, for example, patentapplications No. 61/076,731 (“Method of Forming a Microstructure”) and61/076,736 (“Method of Forming a Patterned Substrate.”)) The actualshape of the channels can be altered to optimize the cross sectionalshape and size that provides the lowest level of optical interferencewhile still ensuring high conductivity and high production yields.

Filled micro-replicated channels can provide a conductor with a highaspect ratio cross section (relative to masked metal films). Thusmaximum conductivity may be achieved with minimum optical visibility,(narrow cross section in the direction of viewing). A method of fillingmicro-replicated channels and desirable shapes of channels with highaspect ratio are described in co-assigned US patent applicationUS2007016081 (Gaides, et. al.).

FIG. 6 shows a cross-profile of a high aspect ratio touch-surface havingmicro-replicated electrodes that are deeper than they are wide. In oneembodiment, a micro-replicated structure that has a ratio of depth towidth greater than 1:1 will yield better performance. Generally, thethinner width of the micro-replicated structure will allow more of thelight exiting the display to pass through the touch sensor. Further,deeper rather than wider channels will reduce the surface area that willlimit reflection of light entering the sensor from the first surface.These advantages are gained while not losing capacitive signal. FIG. 6shows a finger 85 capacitively coupling with a printed copper electrodes87 of touch sensor 86 not only to the top surface but also to the sidesof the sensor.

Micro-contact printing is yet another process that can be used to formmicrocondcutors. Micro-contact printing is the stamping or rotaryprinting of self-assembled monolayer (SAM) patterns on substratesurfaces. The approach exhibits several technologically importantfeatures, including the ability to be carried out for very fine scalepatterns (e.g., feature size of one tenth of a micrometer) and with theextension of the patterned monolayer to the patterning of metals,ceramics, and polymers.

An exemplary micro-contact printing process is as follows:

1. A substrate is coated with metal, (for example, silver or copper issputter coated or plated onto glass or PET film);2. A self-assembled mono-layer mask is stamped onto the platedsubstrate; and,3. Metal coated on the substrate is removed by etching, except for thepattern under the mask.

A micro-contact printing process is described in, for example, U.S. Pat.No. 5,512,131 (Kumar) and in co-pending 3M patent application No.61/032,273 (“Methods of Patterning a Conductor on a Substrate”).Micro-contact printing is generally substrate independent. For example,substrates can be PET, glass, PEN, TAC, or opaque plastic. As is knownin the art, micro-contact printing can be combined with metal depositionprocesses to yield an additive patterning process (for example,including electroless plating).

FIG. 7 a shows a matrix sensor for a small capacitive touch screen. Twopatterns (91 and 92) of electrodes, interconnects, and connector padsare printed on a flexible substrate (for example, PET). The two patternsare then assembled together to form two layers of electrodes on parallelplanes, with electrodes on the top plane orthogonal to conductors on thelower plane as shown (see FIG. 7 b). Sometimes, a shield (not shown) isrequired below the lower electrode plane.

The patterns represented in FIG. 7 may be printed using one of themethods described herein, and a single printing process step was used tosimultaneously print the <10 μm micro-conductors that form electrodes,and the interconnects lines (typically >10 μm) that carry signals fromelectrodes to connector pads, and also the connector pads themselves maybe formed in the same print process. For example, the microcontactprinting process was used to simultaneously print patterns of 3 μmmicroconductors and 500 μm conductive traces 706 as described withrespect to FIG. 27. This particular embodiment yielded severaladvantages:

-   -   1. Alignment of electrodes with interconnects is automatic and        very accurate;    -   2. Interconnects can be printed much narrower and more closely        spaced than with other interconnect printing processes, (for        example, silkscreen printing of conductive inks); and    -   3. The thickness of interconnects (perpendicular to the plane of        the substrate) is much less than with prior interconnect        printing processes, (for example, silkscreen printing of        conductive inks) Thick interconnects cause gaps between        laminated layers which are visible and can undermine the seal        between laminated layers.

FIG. 8 shows the micro-replicated and filled “stock” constructionmaterial with parallel micro-conductors 95 on a substrate 96 surface.Web orientation is verticle (97). The substrate may be PET, PEN, orpolycarbonate, and the micro-conductors may be deposited inmicro-replicated grooves as disclosed herein and/or in 3M patentapplications No. 61/076,731 (“Method of Forming a Microstructure”) and61/076,736 (“Method of Forming a Patterned Substrate”). Spacing ofmicro-conductors is, in one embodiment, preferably between 50 μm and 500μm.

This stock material may be processed into touch sensor components (forexample, electrodes or shields) by interconnecting selectedmicro-conductors with printed (for example, inkjetted, or silkscreened)dielectrics that provide insulating cross-overs whereby post-printed(for example, inkjetted or silkscreened) conductive inks (printed usingthe methods described herein) can bridge over some micro-conductors andmake contact only with selected micro-conductors. Thus interconnects andconnector pads are made for a sensor as shown in FIG. 9, which shows aninkjet-printed dielectric surface 1002 with through-holes 1000 throughthe dielectric, and conductive traces 1001 also printed by inkjet. WhileFIG. 8 and FIG. 9 show micro-conductors printed in the direction of thesubstrate web, it is sometimes advantageous to print micro-conductors ina direction perpendicular to the substrate web.

FIG. 10 shows a cross section of an example of a matrix touch sensorconstructed with two layers of the stock micro-replicatedmicro-conductor material, and two layers of post-printed inkjetconductive traces, separated. The topmost layer 1010 includesmicro-replicated micro-conductors; the next layer 1011 is a printeddielectric; the next layer 1012 includes post-processed conductors; thenext layer 1013 is an adhesive; the next layer 1014 is a post-processedconductor; the next layer 1015 is a printed dielectric, and the finallayer 1016 includes micro-replicated microconductors.

In some embodiments, transparent conductive regions with different sheetresistance in at least one direction are created by including selectivebreaks in conductive traces within an otherwise continuous and uniformmesh. This approach of selective placement of breaks is especiallyuseful for generating articles including patterns of visible transparentconductive regions where the optical transmittance across the article isuniform. The starting mesh can be isotropic or anisotropic. For example,an elongated rectangular transparent conductive bar having a squaremicromesh can be made to exhibit periodic sheet resistance along itslong axis by creating a periodic series of breaks, the breaks being intraces that have a vector component in the direction of the long axisand the periodicity being in the direction of the long axis. Thisperiodicity in sheet resistance can be useful for decoding the positionof an object (e.g., a finger) near the rectangular bar. By selecting thewidth, thickness, and area density of traces, together with thepopulation of breaks, one can design periodic variation in theresistance per unit length along a transparent conductive elementcharacterized by peaks in resistance per unit length that are at least 2times the minimum in resistance per unit length, preferably at least 5times their minimum, more preferably at least 10 times there minimum.

In other embodiments that include selective breaks in an otherwisecontinuous and uniform mesh, the breaks can be placed in order to createapproximately continuously varying sheet resistance in a givendirection. The continuously varying sheet resistance can be useful foramplifying the non-linearity of electric field along a transparentconductive element, beyond that which would be created only by theoverall shape of the element. E.g., as is known in the art, atransparent conductive element with uniform sheet resistance, in theform of an elongated isosceles triangle with an electrical potentialapplied to its base relative to its apex, exhibits non-linear electricfield from base to apex due to the gradient in resistance per unitlength along the field direction (created by the narrowing width of thetriangle). For touch sensors based on interdigitated arrays of suchtriangular transparent conductive elements, it would be advantageous forthe non-linearity in electric field to be even greater, leading togreater signal-to-noise ratio for circuitry used to decode the positionof an object (e.g., a finger) near the array. By selecting the width,thickness, and area density of traces, together with the population ofbreaks, one can design sheet resistance per unit length along atransparent conductive element that increases by a factor of at least1.1 over a distance of 1 centimeter, or at least 1.2, or at least 1.5,or at least 2.

In some embodiments, two transparent conductive regions with differentsheet resistance in at least one direction are created by including ineach of the two regions a contiguous mesh with its own design, each meshnot necessarily including selectively placed breaks. Examples of twomeshes with designs that lead to different values of sheet resistancefor current passing in a single direction, e.g. the x direction in FIG.2, include two meshes with the same thickness (dimension in the zdirection in FIG. 2) of the same conductive material deposit but withdifferent amounts with current-carrying cross-sectional area (y-z planein FIG. 2) per unit width in the y direction. One example of such a pairof mesh regions are two square grid regions each comprising conductivetraces of width 2 micrometers but with different pitch, e.g. 100micrometers and 200 micrometers. Another example of such a pair of meshregions are two rectangular grid regions (non-square, with 100micrometer pitch in the one direction and 200 micrometer pitch in theorthogonal direction) each comprising conductive traces of width 2micrometers but with different orientation, e.g. with the long axes ofthe rectangular cells in the first regions oriented at 90 degrees withrespect to the rectangular cells in the second region.

In some embodiments, the sensors include an insulating visible lighttransparent substrate layer that supports a pattern of conductor, thepattern includes a visible light transparent micropattern region and aregion having a larger feature that is not transparent, wherein thevisible light transparent micropattern region and the larger featureregion include a patterned deposit of the same conductor (e.g., a metal)at approximately the same thickness. The larger feature can take theform of, e.g., a wide conductive trace that makes contact to a visiblelight transparent conductive micropattern region or a pad for makingcontact with an electronic decoding, signal generation, or signalprocessing device. The width of useful larger features, in combinationon the same insulating layer with visible light transparent conductivemicropattern regions, is e.g. between 25 micrometers and 3 millimeters,between 25 micrometers and 1 millimeter, between 25 micrometers and 500micrometers, between 25 micrometers and 250 micrometers, or between 50micrometers and 100 micrometers.

One illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea and a second region micropattern. The electrically conductivemicropattern includes metallic linear electrically conductive featureshaving a thickness of less than 500 nanometers and a width between 0.5and 5 micrometers. The first region micropattern has a first sheetresistance value in a first direction between 5 and 500 ohm per square,is visible light transparent, and has between 95% and 99.5% open area.The second region micropattern has a second sheet resistance value inthe first direction that is different than the first sheet resistancevalue.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 0.5 and 5 micrometers. The first regionmicropattern has an anisotropic first sheet resistance with a differencein sheet resistance values for orthogonal directions of a factor of atleast 1.5, is visible light transparent, and has between 95% and 99.5%open area.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea and a second region micropattern. The electrically conductivemicropattern includes metallic linear electrically conductive featureshaving a thickness of less than 500 nanometers and a width between 1 and4 micrometers. The first region micropattern has a first sheetresistance value in a first direction between 5 and 100 ohm per square,is visible light transparent, and has between 96% and 99.5% open area.The second region micropattern has a second sheet resistance value inthe first direction that is different than the first sheet resistancevalue.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea and a second region micropattern. The electrically conductivemicropattern includes metallic linear electrically conductive featureshaving a thickness of less than 500 nanometers and a width between 0.5and 5 micrometers. The first region micropattern has a first sheetresistance value in a first direction between 5 and 500 ohm per square,is visible light transparent, and has between 95% and 99.5% open area.The second region micropattern has a second sheet resistance value inthe first direction that is different than the first sheet resistancevalue. The micropattern also includes electrically isolated conductordeposits. For all 1 millimeter by 1 millimeter square regions of thesensor that lie in the visible light transparent sensing area, none ofthe regions have a shadowed area fraction that differs by greater than75 percent from the average for all of the regions.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea and a second region micropattern. The electrically conductivemicropattern includes metallic linear electrically conductive featureshaving a thickness of less than 500 nanometers and a width between 0.5and 5 micrometers. The first region micropattern has a first sheetresistance value in a first direction between 5 and 500 ohm per square,is visible light transparent, and has between 95% and 99.5% open area.The second region micropattern has a second sheet resistance value inthe first direction that is different than the first sheet resistancevalue. The micropattern also includes electrically isolated conductordeposits. For all 5 millimeter by 5 millimeter square regions of thesensor that lie in the visible light transparent sensing area, none ofthe regions have a shadowed area fraction that differs by greater than50 percent from the average for all of the regions.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 1 and 4 micrometers. The first regionmicropattern has an anisotropic first sheet resistance with a differencein sheet resistance values for orthogonal directions of a factor of atleast 1.5, is visible light transparent, and has between 96% and 99.5%open area.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 0.5 and 5 micrometers. The first regionmicropattern has an anisotropic first sheet resistance with a differencein sheet resistance values for orthogonal directions of a factor of atleast 1.5, is visible light transparent, and has between 95% and 99.5%open area. The micropattern also includes electrically isolatedconductor deposits. For all 1 millimeter by 1 millimeter square regionsof the sensor that lie in the visible light transparent sensing area,none of the regions have a shadowed area fraction that differs bygreater than 75% from the average for all of the regions.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 0.5 and 5 micrometers. The first regionmicropattern has an anisotropic first sheet resistance with a differencein sheet resistance values for orthogonal directions of a factor of atleast 1.5, is visible light transparent, and has between 95% and 99.5%open area. The micropattern also includes electrically isolatedconductor deposits. For all 5 millimeter by 5 millimeter square regionsof the sensor that lie in the visible light transparent sensing area,none of the regions have a shadowed area fraction that differs bygreater than 50 percent from the average for all of the regions.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The first region micropattern includes metallic linearelectrically conductive features having a width between 0.5 and 5micrometers. The first region micropattern is visible light transparent,and has between 95% and 99.5% open area. For all 1 millimeter by 1millimeter square regions of the first region micropattern, none of thesquare regions have a shadowed area fraction that differs by greaterthan 75 percent from the average for all of the square regions. In oneembodiment the first region micropattern also includes electricallyisolated conductor deposits. In one embodiment, the metallic linearelectrically conductive features have a thickness of less than 500nanometers. In one embodiment, the first region micropattern has a firstsheet resistance value in a first direction between 5 and 100 ohm permeter.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The first region micropattern includes metallic linearelectrically conductive features having a width between 0.5 and 5micrometers. The first region micropattern is visible light transparent,and has between 95% and 99.5% open area. For all 5 millimeter by 5millimeter square regions of the first region micropattern, none of thesquare regions have a shadowed area fraction that differs by greaterthan 50 percent from the average for all of the square regions. In oneembodiment, the metallic linear electrically conductive features have athickness of less than 500 nanometers. In one embodiment, the firstregion micropattern also includes electrically isolated conductordeposits.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 0.5 and 5 micrometers. The first regionmicropattern has a first sheet resistance value in a first directionbetween 5 and 100 ohm per square, is visible light transparent, and hasbetween 95% and 99.5% open area. The micropattern also includeselectrically isolated conductor deposits. For all 1 millimeter by 1millimeter square regions of the sensor that lie in the visible lighttransparent sensing area, none of the regions have a shadowed areafraction that differs by greater than 75 percent from the average forall of the regions.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 0.5 and 5 micrometers. The first regionmicropattern has a first sheet resistance value in a first directionbetween 5 and 100 ohm per square, is visible light transparent, and hasbetween 95% and 99.5% open area. The micropattern also includeselectrically isolated conductor deposits. For all 5 millimeter by 5millimeter square regions of the sensor that lie in the visible lighttransparent sensing area, none of the regions have a shadowed areafraction that differs by greater than 50 percent from the average forall of the regions.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea and a second region micropattern. The electrically conductivemicropattern includes metallic linear electrically conductive featureshaving a thickness of less than 500 nanometers and a width between 0.5and 5 micrometers. The first region micropattern has a first sheetresistance value in a first direction between 5 and 500 ohm per square,is visible light transparent, and has between 95% and 99.5% open area.The second region micropattern has a second sheet resistance value inthe first direction that is different than the first sheet resistancevalue. The sensor also includes larger electrically conductive featuresdisposed on or in the visible light transparent substrate, the largerfeatures comprising a continuous conductor deposit of the same materialand thickness as included in the micropattern and measuring at least 25micrometers in minimum dimension.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 0.5 and 5 micrometers. The first regionmicropattern has an anisotropic first sheet resistance with a differencein sheet resistance values for orthogonal directions of a factor of atleast 1.5, is visible light transparent, and has between 95% and 99.5%open area. The sensor also includes larger electrically conductivefeatures disposed on or in the visible light transparent substrate, thelarger features comprising a continuous conductor deposit of the samematerial and thickness as included in the micropattern and measuring atleast 25 micrometers in minimum dimension.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea and a second region micropattern. The electrically conductivemicropattern includes metallic linear electrically conductive featureshaving a thickness of less than 500 nanometers and a width between 0.5and 5 micrometers. The first region micropattern has a first sheetresistance value in a first direction between 5 and 500 ohm per square,is visible light transparent, and has between 95% and 99.5% open area.The second region micropattern has a second sheet resistance value inthe first direction that is different than the first sheet resistancevalue. The sensor also includes larger electrically conductive featuresdisposed on or in the visible light transparent substrate, the largerfeatures comprising a continuous conductor deposit of the same materialand thickness as included in the micropattern and measuring at least 500micrometers in minimum dimension.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The electrically conductive micropattern includes metallic linearelectrically conductive features having a thickness of less than 500nanometers and a width between 0.5 and 5 micrometers. The first regionmicropattern has an anisotropic first sheet resistance with a differencein sheet resistance values for orthogonal directions of a factor of atleast 1.5, is visible light transparent, and has between 95% and 99.5%open area. The sensor also includes larger electrically conductivefeatures disposed on or in the visible light transparent substrate, thelarger features comprising a continuous conductor deposit of the samematerial and thickness as included in the micropattern and measuring atleast 500 micrometers in minimum dimension.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The first region micropattern includes conductive traces withwidth between 0.5 and 10 micrometers. The first region micropattern isvisible light transparent and has between 90% and 99.95% open area,preferably between 95% and 99.95% open area, and more preferably between97% and 98% open area. For all 5 millimeter by 5 millimeter squareregions of the first region micropattern, none of the square regionshave a shadowed area fraction that differs by greater than 75%,preferably differs by greater than 50%, more preferably differs bygreater than 25%, and most preferably differs by greater than 10% fromthe average for all the square regions. In one embodiment, the firstregion micropattern includes conductive traces with width between 0.5and 5 micrometers, preferably between 1 and 3 micrometers.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The first region micropattern includes conductive traces withwidth between 1 and 10 micrometers. The first region micropattern isvisible light transparent and has between 90% and 99.5% open area. Thefirst region micropattern includes selective breaks in conductive traceswithin an otherwise continuous and uniform mesh.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The first region micropattern includes conductive traces withwidth of about [X+0.5] in units of micrometers and an open area fractionbetween [95−X]% and 99.5%. wherein 0≦X≦4.5. In one embodiment, the touchscreen sensor within the first region micropattern exhibits a haze valueless than 10% and transmission greater than 75%. In another embodimentthe touch screen sensor within the first region micropattern exhibits ahaze value less than 5% and transmission greater than 85%. In oneembodiment, the first region micropattern includes conductive traceswith width of about [98.5−(2.5X÷3.5)]% and [99.5−(X÷3.5)]% wherein0≦X≦3.5.

Another illustrative touch screen sensor includes a visible lighttransparent substrate and an electrically conductive micropatterndisposed on or in the visible light transparent substrate. Themicropattern includes a first region micropattern within a touch sensingarea. The first region micropattern includes parallel conductive tracesspaced 4 mm apart with width of about 9.6 μm, yielding an open areafraction of 99.75%. This embodiment of microreplicated electrodescomprises parallel conductors with a width of about 4 μm, to 10 μm,separated by a distance of 0.5 mm to about 5 mm center to center.Conductors may be formed lengthwise to a web of PET substrate, solengths of conductors may be greater than 1 m. Groups of adjacentconductors may be electrically interconnected to form electrodes of 1 mmto 12 mm total width, for example, using the process described withrespect to FIG. 8 and FIG. 9. Conductors of adjacent electrodes may beinterconnected such that electrodes are interleaved as disclosed in, forexample, co-pending US Patent Application Publication No. 20070074914.

EXAMPLES

The following describe exemplary touch screen sensor designs. They canbe fabricated using known photolithographic methods, e.g. as describedin U.S. Pat. No. 5,126,007 or U.S. Pat. No. 5,492,611. The conductor canbe deposited using physical vapor deposition methods, e.g. sputtering orevaporation, as is known in the art. Unless otherwise noted, theexamples below include conductors patterned by a micro-contact printingtechnique (see technique description above and also co-pending U.S.Patent Application No. 61/032,273). Each conductive pattern exemplifiedherein is useful as a transparent touch screen sensor, when connected todecoding circuitry, as is known in the art (e.g., U.S. Pat. No.4,087,625; U.S. Pat. No. 5,386,219; U.S. Pat. No. 6,297,811; WO2005/121940 A2).

Example 1

A micropattern of thin film gold according to the following descriptionis deposited onto a thin sheet of colorless glass (approximately 1millimeter in thickness). The micropattern 240 is depicted in FIG. 11and FIG. 12. The thickness or height of the gold layer is about 100nanometers. The micropattern 240 involves a series of horizontal(x-axis) mesh bars 241 comprising horizontal narrow traces 242, thetraces 242 measuring approximately 2 micrometers in width. Four of thesehorizontal mesh traces 242 are in electrical communication with a largerfeature contact pad 260. The mesh bars measure approximately 6millimeters in width. Accordingly, with thirteen evenly spaced traces244 traversing a width (y-axis) of 6 millimeters and thirteen evenlyspaced traces 242 traversing a length (x-axis) of 6 millimeters, thepitch of the square grid of traces is 500 micrometers. As depicted inFIG. 12, certain traces have breaks 250, measuring approximately 25micrometers (exaggerated in the figures, for ease in locating). For asquare grid with 2 micrometers wide opaque traces on a 500 micrometerpitch, the fill factor for opaque traces is 0.80%, thus leading to anopen area of 99.20%. For the same square grid, except with a 25micrometer break every 500 micrometers, the fill factor is 0.78%, thusleading to an open area of 99.22%. Thus, the design includes 1 mm×6 mmregions with 99.22% open area and 6 mm×6 mm regions with 99.20% openarea. The average visible transmittance of the glass article with meshis approximately 0.92*0.992=91% (with the factor of 0.92 related tointerfacial reflection losses in light transmission in thenon-conductor-deposited areas of the pattern). Along the horizontal bardirection, there is a series of complete grid regions connected togetherby four traces of gold. Assuming an effective bulk resistivity of 5E-06ohm-cm for sputtered thin film gold, each 2 micrometer wide, 500micrometer long segment of thin film gold has a resistance ofapproximately 125 ohms. The regions with a completed grid, for currentpassing in the direction of the bars, have an effective sheet resistanceof approximately 115 ohms per square. The four traces connecting theregions with completed grids create approximately 62.5 ohms ofresistance between the regions. The above described arrangement ofconductive trace elements leads to a spatially varying resistance perunit length along the bar direction as plotted in FIG. 13. FIG. 14illustrates an equivalent circuit for the array of horizontal mesh bars.The circuit has a series of plates connected by resistors.

Example 2

A micropattern of thin film gold according to the following descriptionis deposited onto a thin sheet of colorless glass (approximately 1millimeter in thickness). The micropattern 340 is depicted in FIG. 15.The thickness of the gold is about 100 nanometers. The micropattern 340has transparent conductive regions in the form of a series ofinterdigitated wedges or triangles. Each wedge is comprised of a meshmade up of narrow metallic traces 342, 344, the traces 342, 344 (seeFIG. 15 a-FIG. 15 c) measuring approximately 2 micrometers in width. Themesh wedges measure approximately 1 centimeter in width at their baseand approximately six centimeters in length. The pitch of the squaregrid of traces 342, 344 is 500 micrometers. Within selected regions ofthe mesh (see FIG. 15 a-FIG. 15 b), within a wedge, breaks 350 measuringapproximately 25 micrometers in length are placed intentionally toaffect the local sheet resistance within the wedge, for current passingalong its long axis. As depicted in FIG. 15 a and FIG. 15 b, regions 15a and 15 b (the regions being separated by approximately 1 centimeter inFIG. 15), breaks 350 are included in the mesh that increase the sheetresistance in the direction of the long axis by a factor greater than1.2. The overall design also includes region 15 c (as depicted in FIG.15 c), which is electrically isolated and spaced apart from regions 15 aand 15 b, and which has a mesh of with sheet resistance value less thanthose of regions 15 a and 15 b. The mesh region 15 c has an open area of99.20%, while the mesh regions 15 a and 15 b have open area fractions of99.20% and 99.21% respectively. The overall design also includes regions15 d and 15 e (as depicted in FIG. 15 d and FIG. 15 e) with meshes oflarger pitch than regions 15 a, 15 b and 15 c, but with the same widthof traces, leading to increased sheet resistance and visibletransmittance.

FIG. 16 illustrates the effect of engineering the mesh properties asdescribed above on the gradient in resistance along a wedge, versus theuse of a standard ITO coating for the same shape of region. The overalldesign also includes larger conductive features in the form ofconductive leads along the left and right sides of the pattern, theleads being approximately 1 millimeter wide and patterned from thin filmgold with approximately 100 nanometers thickness.

Example 3

A transparent sensor element 400 for a touch screen sensor isillustrated in FIG. 17. The sensor element 400 includes two patternedconductor layers 410, 414, (e.g., an X axis layer and a Y axis layer)two optically clear adhesive layers 412, 416, and a base plate 418,laminated together and depicted as separated in FIG. 17 for clarity.Layers 410 and 414 include transparent conductive mesh bars where onelayer is oriented in the x axis direction and the other layer isorientated in the y axis direction, with reference to FIG. 2. The baseplate 418 is a sheet of glass measuring 6 centimeter by 6 centimeters inarea and 1 millimeter in thickness. A suitable optically clear adhesiveis Optically Clear Laminating Adhesive 8141 from 3M Company, St. Paul,Minn. For each of the X-layer and the Y-layer, a clear polymer film witha micropattern of metal is used. A micropattern of thin film goldaccording to the following description is deposited onto a thin sheet ofPET. Suitable PET substrates include ST504 PET from DuPont, Wilmington,Del., measuring approximately 125 micrometers in thickness.

The micropattern 440 is depicted in FIG. 18 and FIG. 19. The thicknessof the gold is about 100 nanometers. The micropattern has transparentconductive regions in the form of a series of parallel mesh bars 442. Inaddition to mesh bars that are terminated with square pads 460(approximately 2 millimeters by 2 millimeters in area, comprisingcontinuous conductor in the form of thin film gold with thicknessapproximately 100 nanometers) for connection to an electronic device forcapacitive detection of finger touch to the base plate, there are meshbars 441 that are electrically isolated from the electronic device. Theisolated mesh bars 441 serve to maintain optical uniformity across thesensor. Each bar is comprised of a mesh made up of narrow metallictraces 443, the traces 443 measuring approximately 5 micrometers inwidth. The mesh bars each measure approximately 2 millimeters in widthand 66 millimeters in length. Within each mesh bar are rectangular cellsmeasuring approximately 0.667 millimeters in width and 12 millimeters inlength. This mesh design serves to provide ties between long-axis tracesin each mesh bar, to maintain electrical continuity along the mesh bar,in case of any open-circuit defects in the long axis traces. However, asopposed to the use of a square mesh with 0.667 millimeter pitch havingsuch ties, the rectangular mesh of FIG. 18 and FIG. 19 trades off sheetresistance along the mesh bar with optical transmittance more optimally.More specifically, the mesh bar depicted in FIG. 18 and FIG. 19 and a 2millimeter wide mesh bar comprising a square mesh with 0.667 millimeterpitch would both have essentially the same sheet resistance along thelong axis of the mesh bar (approximately 50 ohms per square); however,the square grid would occlude 1.5% of the area of the transparentconductive region and the mesh depicted in FIG. 18 and FIG. 19 occludesonly 0.8% of the area of the transparent conductive region.

Example 4

A transparent sensor element for a touch screen sensor is described. Thesensor element includes two patterned conductor layers, two opticallyclear adhesive layers, and a base plate as depicted in FIG. 17. The baseplate is a sheet of glass measuring 6 centimeter by 6 centimeters inarea and 1 millimeter in thickness, laminated together as depicted inFIG. 17. A suitable optically clear adhesive is Optically ClearLaminating Adhesive 8141 from 3M Company. For each of the X-layer andthe Y-layer, a clear polymer film with a micropattern of metal is used.A micropattern of thin film gold according to the following descriptionis deposited onto a thin sheet of PET. Suitable PET substrates includeST504 PET from DuPont, measuring approximately 125 micrometers inthickness.

The micropattern 540 is depicted in FIG. 20 and FIG. 21. The thicknessof the gold is 100 nanometers. The micropattern 540 has transparentconductive regions in the form of a series of parallel mesh bars 542. Inaddition to mesh bars 542 that are terminated with square pads 560 forconnection to an electronic device for capacitive detection of fingertouch to the base plate, there are straight line segments 541 that areelectrically isolated from the electronic device. The straight linesegments 541 lie in regions between the mesh bars 542, with essentiallythe same geometry as the mesh bars, except for approximately 25micrometer breaks 550 as depicted in FIG. 13. The isolated line segments541 serve to maintain optical uniformity across the sensor. Each bar 542is comprised of a mesh made up of narrow metallic traces, the tracesmeasuring approximately 5 micrometers in width. The mesh bars 542 eachmeasure approximately 2 millimeters in width and 66 millimeters inlength. Within each mesh bar 542 are rectangular cells measuringapproximately 0.667 millimeters in width and 12 millimeters in length.The mesh 542 depicted in FIG. 12 and FIG. 13 occludes 0.8% of its areawithin the transparent conductive region. The isolated line segments 541depicted in FIG. 12 and FIG. 13 also occlude 0.8% of the area within theregion they occupy between the mesh bars 542.

Example 5

A transparent sensor element for a touch screen sensor is described. Thesensor element includes two patterned conductor layers, two opticallyclear adhesive layers, and a base plate as depicted in FIG. 17. The baseplate is a sheet of glass measuring 6 centimeter by 6 centimeters inarea and 1 millimeter in thickness, laminated together as depicted inFIG. 17. A suitable optically clear adhesive is Optically ClearLaminating Adhesive 8141 from 3M Company. For each of the X-layer andthe Y-layer, a clear polymer film with a micropattern of metal is used.A micropattern of thin film gold according to the following descriptionis deposited onto a thin sheet of PET. Suitable PET substrates includeST504 PET from DuPont, measuring approximately 125 micrometers inthickness.

The micropattern 640 is depicted in FIG. 22 and FIG. 23. The thicknessof the gold is about 100 nanometers. The micropattern 640 hastransparent conductive regions in the form of a series of parallel meshbars 642. In addition to mesh bars 642 that are terminated with squarepads 660 for connection to an electronic device for capacitive detectionof finger touch to the base plate, there are straight line segments 641that are electrically isolated from the electronic device. The straightline segments 641 lie in regions between the mesh bars, with a similargeometry to the line segments of the mesh bars. The electricallyisolated line segments 641 serve to maintain optical uniformity acrossthe sensor. Each bar 641, 642 is comprised of narrow metallic traces,the traces measuring approximately 3 micrometers in width. The mesh bars642 each measure approximately 2 millimeters in width and 66 millimetersin length. Within each mesh bar 642 comprising randomly shaped cells.The mesh 642 depicted in FIG. 22 and FIG. 23 occludes less than 5percent of its area within the transparent conductive region. Theisolated line segments 641 depicted in FIG. 22 and FIG. 23 also occludeless than 5 percent of the area within the region they occupy betweenthe mesh bars.

Preparation of Metalized Polymer Film Substrates e.g.s 6 Through 40

A polymer film substrate was provided, polyethyleneterephthalate (PET)(ST504, E.I. DuPont de Nemours and Company, Wilmington, Del.). Theoptical properties of the ST504 PET film were determined by Haze-Gard.The haze and the transmission measured approximately 0.67% and 92.9%,respectively.

Some substrate films were coated with gold and some were coated withsilver. The gold-coated substrates were prepared by thermal evaporation(DV-502A, Denton Vacuum, Moorestown, N.J.). For gold-coated substrates,the substrate surface was first coated with 20 angstroms of chromium andthen coated with 100 nanometers of gold. In the case of silver-coatedsubstrates, two different methods were used. Some silver-coatedsubstrates were prepared by both thermal evaporation (DV-502A, DentonVacuum, Moorestown, N.J.) and some were prepared by sputtering (3M). Thesubstrate surface was coated with 100 nanometers of silver in all cases.

Stamp Fabrication

Two different master tools for molding elastomeric stamps were generatedby preparing patterns of photoresist (Shipley 1818, Rohm and HaasCompany, Philadelphia, Pa.) on 10-centimeter diameter silicon wafersusing photolithography. The different master tools were based on twodifferent mesh shapes, herein referred to as “Hex” and “Square”. Hexrefers to a pattern comprising a network of lines that define enclosedareas having the shape of a regular hexagon. Square refers to a patterncomprising a network of lines that define enclosed areas having theshape of squares. An elastomeric stamp was molded against the mastertool by pouring uncured polydimethylsiloxane (PDMS, Sylgard™ 184, DowCorning, Midland Mich.) over the tool to a thickness of approximately3.0 millimeters. The uncured silicone in contact with the master wasdegassed by exposing to a vacuum, and then cured for 2 hours at 70° C.After peeling from the master tool, a PDMS stamp was provided with arelief pattern comprising raised features approximately 1.8 micrometersin height. For both hex mesh and square mesh stamps, the raised featuresof were the lines defining the respective mesh geometry, as describedabove.

Inking

The stamp was inked by contacting its back side (flat surface withoutrelief pattern) to a solution of octadecylthiol (“ODT” O0005, TCIAMERICA, Wellesley Hills, Mass.) in ethanol for 20 hours. 10 mM of ODTsolution was used for the stamp with square mesh pattern, and 5 mM ofODT solution was used for the stamp with hex mesh pattern.

Stamping

Metalized polymer film substrates were stamped with inked stamps asdescribed above. For stamping, the metalized film was contacted to thestamp relief patterned-surface, which was face up, by first contactingan edge of the film sample to the stamp surface and then rolling thefilm into contact across the stamp, using a foam roller with diameter ofapproximately 3.0 centimeters. The rolling step required less than 1second to execute. After rolling step, the substrate was contacted withthe stamp for 10 seconds. Then, the substrate was peeled from the stamp,a step that required less than 1 second.

Etching

After stamping, the metallized film substrate with printed pattern wasimmersed into an etchant solution for selective etching and metalpatterning. For printed metalized film substrates bearing a gold thinfilm, the etchant comprised 1 gram of thiourea (T8656, Sigma-Aldrich,St. Louis, Mo.), 0.54 milliliter of concentrated hydrochloric acid(HX0603-75, EMD Chemicals, Gibbstown, N.J.), 0.5 milliliter of hydrogenperoxide (30%, 5240-05, Mallinckrodt Baker, Phillipsburg, N.J.), and 21grams of deionized water. To pattern the gold thin film, the printedmetalized film substrate was immersed in the etch solution for 50seconds. For printed metalized film substrates bearing a silver thinfilm, the etchant comprised 0.45 grams of thiourea (T8656,Sigma-Aldrich, St. Louis, Mo.), 1.64 grams of ferric nitrate (216828,Sigma-Aldrich, St. Louis, Mo.), and 200 milliliter of deionized water.To pattern the silver thin film, the printed metalized film substratewas immersed in the etch solution for 3 minutes. After patterned etchingof the gold, residual chromium was etched using a solution of 2.5 gramsof potassium permanganate (PX1551-1, EMD Chemicals, Gibbstown, N.J.), 4grams of potassium hydroxide (484016, Sigma-Aldrich, St. Louis, Mo.),and 100 milliliters of deionized water.

Characterization

After selective etching and metal patterning, the metal patterns werecharacterized using an optical microscope (Model ECLIPSE LV100D equippedwith a DS-Fil digital camera and NIS-Elements D software, Nikon,Melville, N.Y.), scanning electron microscope (SEM, Model JSM-6400, JEOLLtd, Tokyo, Japan), and Haze-Gard (Haze-Gard plus, BYK Gardner,Columbia, Md.). The microscopic techniques were used to determine thewidth of line features in the metal pattern. Haze-Gard was used todetermine the transmission and the haze for the mesh-grid coated films.The Haze-Gard measurements were done after laminating the patterned filmon a glass with an optical clear adhesive (3M Product). The visibilityfactor of high, medium, and low was assigned to describe the degree ofvisibility of line features in the metal pattern (human observation withunaided eye).

Example 6

A hexagonal mesh grid pattern of thin film gold was fabricated andcharacterized according to the procedures described above. The inksolution comprised octadecylthiol dissolved in ethanol at aconcentration of 5 mM. The ink solution was contacted to the back sideof the stamp for 20 hours. The stamping time was 10 seconds. FIG. 1gives an SEM photomicrograph recorded from the completed thin film goldmicropattern. The actual line width measured approximately 1.63micrometers. The percentage of open area was recalculated based on themeasured line width and the designed edge-to-edge width of 400micrometers, which is 99.2%. The optical properties of the gold Hex meshgrid coated film were determined by Haze-Gard. The haze and thetransmission measured approximately 1.14% and 91.6%, respectively. Highvisibility was assigned to this example because the gold Hex meshpattern with a line width of 1.63 micrometers and an edge-to-edge widthof 400 micrometers can be easily seen.

Examples 7 to 15

Hexagonal mesh grid patterns of thin film gold were fabricated andcharacterized according to the procedures described in Example 1. Theactual line width for each example was measured using SEM and listed inTable 1. The percentage of open area was then recalculated based on theactual line width and designed edge-to-edge width and listed in Table 1.Table 1 also gives the haze value and the transmission value for eachexample measured by Haze-Gard and the visibility factors assigned toeach example.

Example 16

A square mesh grid pattern of thin film gold was fabricated andcharacterized according to the procedures described above. The inksolution comprised octadecylthiol dissolved in ethanol at aconcentration of 10 mM. The ink solution was contacted to the back sideof the stamp for 20 hours. The stamping time was 10 seconds. The actualline width measured approximately 4.73 micrometers using opticalmicroscope. The percentage of open area was recalculated based on themeasured line width and the designed pitch of 320 micrometers, which is97.0%. The optical properties of the gold Square mesh grid coated filmwere determined by Haze-Gard. The haze and the transmission measuredapproximately 1.58% and 88.6%, respectively. High visibility wasassigned to this example because the gold Square mesh pattern with aline width of 4.73 micrometers and a pitch of 320 micrometers can beeasily seen.

Examples 17-23

Square mesh grid patterns of thin film gold were fabricated andcharacterized according to the procedures described in Example 11. Theactual line width for each example was measured using optical microscopeand listed in Table 1. The percentage of open area was then recalculatedbased on the actual line width and designed pitch and listed in Table 1.Table 1 also gives the haze value and the transmission value for eachexample measured by Haze-Gard and the visibility factors assigned toeach example.

Example 24

A hex mesh grid pattern of thin film silver was fabricated andcharacterized according to the procedures described above. Thesilver-coated substrates were prepared by sputtering. The ink solutioncomprised octadecylthiol dissolved in ethanol at a concentration of 5mM. The ink solution was contacted to the back side of the stamp for 20hours. The stamping time was 10 seconds. FIG. 2 gives an SEMphotomicrograph recorded from the completed thin film silvermicropattern. The actual line width measured approximately 2.43micrometers. The percentage of open area was recalculated based on themeasured line width and the designed edge-to-edge width of 600micrometers, which is 99.2%. The optical properties of the gold Hex meshgrid coated film were determined by Haze-Gard. The haze and thetransmission measured approximately 1.19% and 91.8%, respectively. Highvisibility was assigned to this example because the silver Hex meshpattern with a line width of 2.43 micrometers and an edge-to-edge widthof 600 micrometers can be easily seen.

Examples 25 to 32

Hex mesh grid patterns of thin film silver were fabricated andcharacterized according to the procedures described in Example 19. Theactual line width for each example was measured using SEM and listed inTable 1. The percentage of open area was then recalculated based on theactual line width and designed edge-to-edge width and listed in Table 1.Table 1 also gives the haze value and the transmission value for eachexample measured by Haze-Gard and the visibility factors assigned toeach example.

Example 33

A Square mesh grid pattern of thin film silver was fabricated andcharacterized according to the procedures described above. Thesilver-coated substrates were prepared by thermal evaporation. The inksolution comprised octadecylthiol dissolved in ethanol at aconcentration of 10 mM. The ink solution was contacted to the back sideof the stamp for 20 hours. The stamping time was 10 seconds. The actualline width measured approximately 5.9 micrometers using opticalmicroscope. The percentage of open area was recalculated based on themeasured line width and the designed pitch of 320 micrometers, which is96.3%. The optical properties of the silver Square mesh grid coated filmwere determined by Haze-Gard. The haze and the transmission measuredapproximately 1.77% and 88.9%, respectively. High visibility wasassigned to this example because the silver Square mesh pattern with aline width of 5.9 micrometers and a pitch of 320 micrometers can beeasily seen.

Examples 34-40

Square mesh grid patterns of thin film silver were fabricated andcharacterized according to the procedures described in Example 28. Theactual line width for each example was measured using optical microscopeand listed in Table 1. The percentage of open area was then recalculatedbased on the actual line width and designed pitch and listed in Table 1.Table 1 also gives the haze value and the transmission value for eachexample measured by Haze-Gard and the visibility factors assigned toeach example.

TABLE 1 Example Metal Mesh Line width Open area Haze TransmissionVisibility number type geometry (μm) fraction (%) (%) (%) of LinesRegion¹ 6 Gold Hex 1.63 99.2 1.14 91.6 High 2 7 Gold Hex 2.92 99.0 1.0491.6 High 2 8 Gold Hex 2.91 99.0 1.2 91.5 High 2 9 Gold Hex 1.92 98.71.37 91.4 Medium 1 10 Gold Hex 2.14 97.9 1.61 91.2 Low 1 11 Gold Hex1.84 98.2 1.62 90.9 Low 1 12 Gold Hex 2.65 98.2 1.42 90.8 Medium 1 13Gold Hex 2.69 97.3 1.76 90.6 Low 1 14 Gold Hex 1.13 97.7 2.57 90.3 Low 215 Gold Hex 2.27 97.7 1.78 90.3 Low 1 16 Gold Square 4.73 97.0 1.58 88.6High 2 17 Gold Square 3.01 96.2 2.33 88.4 Medium 2 18 Gold Square 4.794.1 1.95 86.0 Medium 2 19 Gold Square 3.01 92.5 3.77 85.6 Low 2 20 GoldSquare 4.49 91.4 2.77 83.3 Low 2 21 Gold Square 3.18 87.3 5.45 81.1 Low3 22 Gold Square 4.73 88.2 3.11 80.9 Low 3 23 Gold Square 2.82 86.9 6.6879.1 Low 3 24 Silver Hex 2.43 99.2 1.19 91.8 High 2 25 Silver Hex 2.1899.3 1.45 91.7 High 2 26 Silver Hex 1.92 99.0 1.39 91.5 High 2 27 SilverHex 2.44 98.4 1.62 91.3 Medium 1 28 Silver Hex 0.94 99.1 1.92 91.2 Low 129 Silver Hex 2.18 98.6 1.92 91.0 Medium 1 30 Silver Hex 2.55 97.5 1.9390.8 Low 1 31 Silver Hex 1.81 98.2 1.96 90.7 Low 1 32 Silver Hex 2.8997.1 2.04 90.0 Low 1 33 Silver Square 5.9 96.3 1.77 88.9 High 3 34Silver Square 3.35 95.8 2.46 88.0 Medium 2 35 Silver Square 5.57 93.12.55 86.2 Medium 3 36 Silver Square 2.76 93.1 3.99 85.0 Low 2 37 SilverSquare 5.74 89.1 3.49 83.6 Low 3 38 Silver Square 5.7 85.8 4.09 80.8 Low3 39 Silver Square 2.98 88.1 5.69 80.2 Low 3 40 Silver Square 2.78 87.17.0 77.6 Low 3 ¹Region refers to the different regions as shown andlabeled in FIG. 24.

Example 41

A transparent sensor element was fabricated and combined with a touchsensor drive device as generally shown in FIGS. 27, 28 and 29. Thedevice was then integrated with a computer processing unit connected toa display to test the device. The device was able to detect thepositions of multiple single and or simultaneous finger touches, whichwas evidenced graphically on the display. This example usedmicro-contact printing and etching techniques (see also co-pending U.S.Patent App. No. 61/032,273) to form the micro-conductor pattern used inthe touch sensor.

Formation of a Transparent Sensor Element

First Patterned Substrate

A first visible light substrate made of polyethylene terephthalate (PET)having a thickness of 125 micrometers (μm) was vapor coated with 100 nmsilver thin film using a thermal evaporative coater to yield a firstsilver metalized film. The PET was commercially available as productnumber ST504 from E.I. du Pont de Nemours, Wilmington, Del. The silverwas commercially available from Cerac Inc., Milwaukee, Wis. as 99.99%pure 3 mm shot.

A first poly(dimethylsiloxane) stamp, referred to as PDMS andcommercially available as product number Sylgard 184, Dow Chemical Co.,Midland, Mich., having a thickness of 3 mm, was molded against a 10 cmdiameter silicon wafer (sometimes referred to in the industry as a“master”) that had previously been patterned using standardphotolithography techniques. The PDMS was cured on the silicon wafer at65° C. for 2 hours. Thereafter, the PDMS was peeled away from the waferto yield a first stamp having two different low-density regions withpatterns of raised features, a first continuous hexagonal mesh patternand a second discontinuous hexagonal mesh pattern. That is, the raisedfeatures define the edges of edge-sharing hexagons. A discontinuoushexagon is one that contains selective breaks in a line segment. Theselective breaks had a length less than 10 μm. The breaks were designedand estimated to be approximately 5 μm. In order to reduce theirvisibility, it found that, preferably, the breaks should be less than 10μm, more preferably, 5 μm or less, e.g., between 1 and 5 μm. Each raisedhexagon outline pattern had a height of 2 μm, had 1% to 3% areacoverage, corresponding to 97% to 99% open area, and line segments thatmeasured from 2 to 3 μm in width. The first stamp also included raisedfeatures defining 500 μm wide traces. The first stamp has a firststructured side that has the hexagonal mesh pattern regions and thetraces and an opposing second substantially flat side.

The stamp was placed, structured side up, in a glass Petri dishcontaining 2 mm diameter glass beads. Thus, the second, substantiallyflat side was in direct contact with the glass beads. The beads servedto lift the stamp away from the base of the dish, allowing the followingink solution to contact essentially all of the flat side of the stamp. A10 millimolar ink solution of 1-octadecanethiol (product number C18H3CS,97%, commercially available from TCI America, Portland Oreg.) in ethanolwas pipetted into the Petri dish beneath the stamp. The ink solution wasin direct contact with the second substantially flat side of the stamp.After sufficient inking time (e.g., 3 hours) where the ink has diffusedinto the stamp, the first stamp was removed from the petri dish. Theinked stamp was placed, structured side up, onto a working surface. Thefirst silver metalized film was applied using a hand-held roller ontothe now inked structured surface of the stamp such that the silver filmwas in direct contact with the structured surface. The metalized filmremained on the inked stamp for 15 seconds. Then the first metalizedfilm was removed from the inked stamp. The removed film was placed forthree minutes into a silver etchant solution, which contained (i) 0.030molar thiourea (product number T8656, Sigma-Aldrich, St. Louis, Mo.) and(ii) 0.020 molar ferric nitrate (product number 216828, Sigma-Aldrich)in deionized water. After the etching step, the resulting firstsubstrate was rinsed with deionized water and dried with nitrogen gas toyield a first patterned surface. Where the inked stamp made contact withthe silver of the first metalized substrate, the silver remained afteretching. Thus silver was removed from the locations where contact wasnot made between the inked stamp and silver film.

FIGS. 27, 27 a and 27 b show a first patterned substrate 700 having aplurality of first continuous regions 702 alternating between aplurality of first discontinuous regions 704 on a first side of thesubstrate, which is the side that contained the now etched and patternedsilver metalized film. The substrate has an opposing second side that issubstantially bare PET film. Each of the first regions 702 has acorresponding 500 μm wide conductive trace 706 disposed at one end. FIG.27 a shows an exploded view of the first region 702 having a pluralityof continuous lines forming a hexagonal mesh structure. FIG. 27 b showsan exploded view of the first discontinuous region 704 having aplurality of discontinuous lines (shown as selective breaks in eachhexagon) forming a discontinuous hexagonal mesh structure. Each meshstructure of regions 702 and 704 had 97% to 99% open area. Each linesegment measured from 2 to 3 μm.

Second Patterned Substrate

The second patterned substrate was made as the first patterned substrateusing a second visible light substrate to produce a second silvermetalized film. A second stamp was produced having a second continuoushexagonal mesh pattern interposed between a second discontinuoushexagonal mesh pattern.

FIGS. 28, 28 a and 28 b show a second patterned substrate 720 having aplurality of second continuous regions 722 alternating between aplurality of second discontinuous regions 724 on a first side of thesecond substrate. Each of the second regions 722 has a corresponding 500μm wide second conductive trace 726 disposed at one end. FIG. 28 a showsan exploded view of one second region 722 having a plurality ofcontinuous lines forming a hexagonal mesh structure. FIG. 28 b shows anexploded view of one second discontinuous region 724 having a pluralityof discontinuous lines (shown as selective breaks in each hexagon)forming discontinuous hexagonal mesh structure. The selective breaks hada length less than 10 μm. The breaks were designed and estimated to beapproximately 5 μm. In order to reduce their visibility, it found that,preferably, the breaks should be less than 10 μm, more preferably, 5 μmor less, e.g., between 1 and 5 μm. Each mesh structure of region 722 and724 had 97% to 99% open area. Each line segment measured from 2 to 3 μm.

Formation of a Projected Capactive Touch Screen Sensor Element

The first and second patterned substrates made above were used toproduce a two-layer projected capacitive touch screen transparent sensorelement as follows.

The first and second patterned substrates were adhered together usingOptically Clear Laminating Adhesive 8141 from 3M Company, St. Paul,Minn. to yield a multilayer construction. A handheld roller was used tolaminate the two patterned substrates with the regions of the first andsecond conductive trace regions 706 and 726 being adhesive free. Themultilayer construction was laminated to a 0.7 mm thick float glassusing Optically Clear Laminating Adhesive 8141 such that the first sideof the first substrate was proximate to the float glass. The adhesivefree first and second conductive trace regions 706 and 726 allowedelectrical connection to be made to the first and second patternedsubstrates 700 and 720.

FIG. 29 shows a top plan view of a multilayer touch screen sensorelement 740 where the first and second patterned substrate have beenlaminated. Region 730 represented the overlap of the first and secondcontinuous regions. Region 732 represented the overlap of the firstcontinuous region and the second discontinuous region. Region 734represented the overlap of the second continuous region and the firstdiscontinuous region. And, region 736 represented the overlap betweenthe first and second discontinuous regions. While there was a pluralityof these overlap regions, for ease of illustration, only one region ofeach has been depicted in the figure.

The integrated circuits used to make mutual capacitance measurements ofthe transparent sensor element were PIC18F87J10 (Microchip Technology,Chandler, Ariz.), AD7142 (Analog Devices, Norwood, Mass.), andMM74HC154WM (Fairchild Semiconductor, South Portland, Me.). ThePIC18F87J10 was the microcontroller for the system. It controlled theselection of sensor bars which MM74HC154WM drives. It also configuredthe AD7142 to make the appropriate measurements. Use of the systemincluded setting a number of calibration values, as is known in the art.These calibration values can vary from touch screen to touch screen. Thesystem could drive 16 different bars and the AD7142 can measure 12different bars. The configuration of the AD7142 included selection ofthe number of channels to convert, how accurately or quickly to takemeasurements, if an offset in capacitance should be applied, and theconnections for the analog to digital converter. The measurement fromthe AD7142 was a 16 bit value representing the capacitance of the crosspoint between conductive bars in the matrix of the transparent sensorelement.

After the AD7142 completed its measurements it signaled themicrocontroller, via an interrupt, to tell it to collect the data. Themicrocontroller then collected the data over the SPI port. After thedata was received, the microcontroller incremented the MM74HC154WM tothe next drive line and cleared the interrupt in the AD7142 signaling itto take the next set of data. While the sampling from above wasconstantly running, the microcontroller was also sending the data to acomputer with monitor via a serial interface. This serial interfaceallowed a simple computer program, as are known to those of skill in theart, to render the raw data from the AD7142 and see how the values werechanging between a touch and no touch. The computer program rendereddifferent color across the display, depending on the value of the 16 bitvalue. When the 16 bit value was below a certain value, based on thecalibration, the display region was rendered white. Above thatthreshold, based on the calibration, the display region was renderedgreen. The data were sent asynchronously in the format of a 4 byteheader (0xAAAAAAAA), one byte channel (0x00-0x0F), 24 bytes of data(represents the capacitive measurements), and carriage return (0x0D).

Results of Testing of the System

The transparent sensor element was connected to the touch sensor drivedevice. When a finger touch was made to the glass surface, the computermonitor rendered the position of touch that was occurring within thetouch sensing region in the form of a color change (white to green) inthe corresponding location of the monitor. When two finger touches weremade simultaneously to the glass surface, the computer monitor renderedthe positions of touches that were occurring within the touch sensingregion in the form of a color change (white to green) in thecorresponding locations of the monitor. When three finger touches weremade simultaneously to the glass surface, the computer monitor renderedthe positions of touches that were occurring within the touch sensingregion in the form of a color change (white to green) in thecorresponding locations of the monitor.

Example 42

One embodiment of microreplicated electrodes comprises parallelconductors with a width of about 0.5 to about 5 microns (Y dimension inFIG. 5), separated by a distance of about 2 mm to about 5 mm center tocenter. Groups of adjacent conductors may be electrically interconnectedto form electrodes of 1 mm to 10 mm total width, for example, using theprocess described with respect to FIG. 8 and FIG. 9.

The traces were made by forming rectangular microreplicated grooves 10μm wide (X dimension in FIG. 5), 20 μm deep (Z dimension in FIG. 5),spaced 4 mm apart on a transparent substrate of PET using methodsdescribed herein and by reference. The parallel array of grooves was 100mm wide. Grooves were printed in the PET web direction so their lengthwas the length of the web, (>20 meters).

Grooves were filled with a seed ink manufactured by Conductive InkjetTechnologies, (CIT). A thin layer of ink was smoothed over the groovesthen excess was removed with a doctor blade in a process similar to silkscreening. The seed ink was then cured using UV light. The substratewith ink-filled grooves was then electroless plated with copper. Theresulting microconductors were each approximately 9.6 μm wide. The inkfilling, UV curing, and electroless plating process was performed byCIT. Microconductors with substrates with grooves <10 μm wide, 20 μmdeep, spaced 2 mm were also made using the process described.

Visually Obscuring the Conductive Micropattern Elements

In some of the embodiments herein described, it is desirable to takeadditional measures to reduce the visibility of the conductivemicropattern elements. Despite their small size, when patterned incertain ways, and when exposed sometimes to particular lightingconditions, it may be possible for a user to discern features of theconductive micropattern. For example, conductive micropattern elementsmay be rendered less visible by reducing their width to less than 10micrometers, but they may still produce moiré patterns due to opticalinterference with the regular spacing of display pixels from, forexample, a liquid crystal display (LCD) or an organic light emittingdiode (OLED) display.

In some embodiments, the micropattern may have pseudo-random variations.The term pseudo-random describes variation in the micropattern from anotherwise regular geometry. Regular geometries include straight lines inthe case of one dimensional conductor elements and arrays of patternfeatures having translational symmetry on a short length scale (forexample, on the scale of one to two cells) in the case of twodimensional conductor elements (for example, meshes). Pseudo-randomvariation refers to the non-regular perturbation of one dimensional ortwo dimensional conductor elements. Thus, pseudo-random one dimensionalconductor elements are not straight lines, but rather they deviate fromstraightness in a way that, on at least some length scale, is notperiodic. Pseudo-random two dimensional conductor elements are notmeshes composed of a single cell geometry or a small number of cellgeometries (for example, two or four) that repeat regularly in twodimensions, but rather they include many cells in proximity (forexample, greater than 10 or greater than 100) that vary in shape. Theterm random as used herein refers to such a lack of regularity as justdescribed, and may be the result of i) a process that yields trulyrandom micropattern geometry (that is, the geometry varies in randomfashion from one article to the next), or ii) a process that yields adefined geometry that is the same from one article to the next, but thatdeviates intentionally from regularity. The latter of these twodescriptions relates to pseudo-random variation.

FIG. 30 shows a magnified view of pixels 58 with straight microconductor61 and, a first randomly curved micro-conductor 63, and a secondrandomly curved microconductor 62. Also shown is LCD mask line 59.Microconductor 61 will cause visible interference with the displaypixels, because it blocks one color over a significant distance, and itsnear but imperfect alignment with the vertical columns of pixel elementsin the LCD may cause visible interference. Micro-conductor 63 isgenerally less noticeable than micro-conductor 61 because it bendspseudo-randomly to obscure different colors of pixels in a vertical row.Microconductor 62 bends pseudo-randomly so it does not align withdisplay pixels. The period (length) of bends ensures that, on average,line 62 will cross from one pixel to another or from one pixel color toanother within a few pixels distance, avoiding visually apparentpatterns. Bends in line 63 are larger in amplitude so line 63 intersectsseveral parallel rows of pixels.

Another method of reducing the visibility of the conductive micropatternelements is to place them behind (relative to a viewer of the display)some type of a substrate or coating having one or more features thatobscure or reduce the visibility of the micropattern or microconductors.This technique could be used on its own or in combination with thetechniques described above regarding random changes in themicroconductor's path.

FIG. 31 illustrates a micropattern obscuring feature 267 positionedbetween a finger 85 (or viewer) and a micropatterned microconductor 269.Finger 85 is shown capacitively coupling to the micropatterenedmicroconductor 269. Micropattern obscuring feature 267 could be acoating, or an additional substrate. The various elements shown in FIG.31 may be contained on separate substrates, or they could merely belayers on a single substrate. It could be part of substrate 268 (whichincludes micropatterned microconductor 269); it will preferably bepositioned between the user or viewer and the micropatterenedmicroconductor. There may be one or more additional layers (such asadhesive layers) or substrates between the micropattern obscuringfeature 267 and the micropatterned microconductor. Display 270 ispositioned below substrate 268. There may be one or more layers orsubstrates between substrate 268 and display 270. Display 270 may be anydisplay upon which a touch sensing device may be affixed, such as forexample an LCD display or an OLED display. FIG. 31 shows only oneexemplary configuration of how a micropattern obscuring feature may beemployed to reduce the visibility of a microconductor. Depending on thetype of display (for example a rear projection display), themicropattern obscuring feature may be modified accordingly, mutatismutandis.

In one embodiment, micropattern obscuring feature 267 is an anti-glaresurface. An anti-glare (AG, or matte) finish on the surface over adisplay is often used to scatter reflected light, making the displayedlight (from display 270) more viewable. An anti-glare surface has theside effect of scattering the light from the display also, so resolutionof displayed images is in some embodiments reduced. An anti-glaresurface is generally made by forming random surface structures (forexample, bumps) on the outer-most surface over a display, either byetching the surface or by coating it with a material that forms surfacestructures of transparent material. Each surface structure acts as alens or facet, depending on the shape of the structure, so any opticalfeature under a surface structure will be diffracted in a randomdirection.

The degree of display resolution reduction from an anti-glare finish maybe mitigated by minimizing the size of surface structures to besignificantly less than the dimensions of display pixel elements.Typical anti-glare surface structures have randomly or pseudo-randomlyvarying shapes with dimensions averaging 10 μm to 20 μm (see, forexample, US patent application 2006/0046078.) Such structures may thenbe less than 10% of the size of a typical LCD display pixel, but wouldbe larger than the width of typical conductive micropattern element asdescribed herein, so an anti-glare surface can, in some embodiments,render conductive micropattern elements (microconductors) un-resolvableby the human eye, while minimally affecting a displayed image. Commontests for display resolution include the USAF 1951 resolution target andthe EIA 1956 video resolution target, both of which comprise sets offine parallel lines of various width and pitch. The minimum resolvablepitch (lines/meter) is a measure of resolution. By these measurements, 1μm to 10 μm microconductors will be un-resolvable behind many anti-glaresurfaces commonly used for displays, especially when themicroconductors' line spacing is randomized as in FIG. 30, and spacingis much further apart than the standard test methods cited above.

Generally, anti-glare surface structures should be in the range of 20%to 200% of the visible cross section of the microconductors. This iseasy to achieve with printed microconductors discussed herein, and itcan also be achieved with 10 μm to 25 μm diameter micro-wire electrodesdescribed in, for example, U.S. Pat. No. 6,137,427 (Binstead).

Some display technologies, for example rear projection displays (andfront projection displays), may project through or onto a surface thathas light diffusing properties. A diffusing surface is similar to an AGsurface in that it scatters light, but it is translucent with a higherhaze value. The properties of these surfaces may be similar to AGsurfaces discussed above, including the relative sizes of typicalsurface structures. So, microconductor sensor electrodes embedded in arear projection display may also be optically obscured by the AG surfaceand/or diffusing properties of a surface or substrate.

In another embodiment, micropattern obscuring feature 267 is a polarizeror contrast-enhancing filter. Microconductors overlaid on a display havepossible optical effects including reduction of light transmission,moiré patterns, and reflection of ambient light. Reflection can bereduced by placing a touch sensor behind the front polarizer of an LCD.See, for example, U.S. Pat. No. 6,395,863 (Geaghan). For example, amicroconductor-based matrix capacitive touch screen or magneticdigitizer (constructed on a birefringent substrate such as castpolycarbonate) may be laminated under the front polarizer of an LCD.Most polarizers are made of laminated layers, (for example, iodine dopedpolyvinylalcohol (PVA) sandwiched between two sheets of TAC (cellulosetriacetate)). Electrodes of a microconductor based capacitive touchscreen or magnetic digitizer can be printed directly onto one or more ofthe layers of a polarizer prior to laminating the polarizer sheetstogether. A hardcoat barrier coat may be applied to TAC prior toprinting of microconductors. A sensor including the microconductorelectrodes may be placed behind a contrast enhancement filter, (forexample, 40% gray filter) to reduce the optical effect of reflectedlight from microconductors.

To minimize interference with the pixel pattern of the display and toavoid view ability of the pattern elements (for example, conductorlines) by the naked eye of a user or viewer, the minimum dimension ofthe conductive pattern elements (for example, the width of a line orconductive trace) should be less than or equal to approximately 50micrometers, or less than or equal to approximately 25 micrometers, orless than or equal to approximately 10 micrometers, or less than orequal to approximately 5 micrometers, or less than or equal toapproximately 4 micrometers, or less than or equal to approximately 3micrometers, or less than or equal to approximately 2 micrometers, orless than or equal to approximately 1 micrometer, or less than or equalto approximately 0.5 micrometer.

In some embodiments, the minimum dimension of conductive patternelements is between 0.5 and 50 micrometers, in other embodiments between0.5 and 25 micrometers, in other embodiments between 1 and 10micrometers, in other embodiments between 1 and 5 micrometers, in otherembodiments between 1 and 4 micrometers, in other embodiments between 1and 3 micrometers, in other embodiments between 0.5 and 3 micrometers,and in other embodiments between 0.5 and 2 micrometers. With respect tothe reproducible achievement of useful optical properties (for examplehigh transmission and invisibility of conductive pattern elements withthe naked eye) and electrical properties, and in light of the constraintof using practical manufacturing methods, preferred values of minimumdimension of conductive pattern elements are between 0.5 and 5micrometers, more preferably between 1 and 4 micrometers, and mostpreferably between 1 and 3 micrometers.

In general, the deposited electrically conductive material reduces thelight transmission of the touch sensor, undesirably. Basically, whereverthere is electrically conductive material deposited, the display isshadowed in terms of its viewability by a user. The degree ofattenuation caused by the conductor material is proportional to the areafraction of the sensor or region of the sensor that is covered byconductor, within the conductor micropattern.

One skilled in the art will appreciate that the present invention can bepracticed with embodiments other than those disclosed. The disclosedembodiments are presented for purposes of illustration and notlimitation, and the present invention is limited only by the claims thatfollow.

1. A touch screen sensor having a touch-sensitive surface comprising:within a touch sensing area, a electrically conductive micropatterndisposed on or in a visible light transparent substrate, wherein themicropattern includes conductive traces with width between about 1 and10 micrometers; and one or more light scattering elements in anoptically continuous layer of substantially uniform optical densitydisposed between the micropattern and the touch-sensitive surface, andwherein the light scattering elements comprise microscopic featureshaving a size greater than the width of the conductive traces.
 2. Thetouch screen sensor of claim 1, wherein the optically continuous layeris associated with a substrate other than the visible light transparentsubstrate.
 3. The touch screen sensor of claim 1, wherein the opticallycontinuous layer comprises a polarizer.
 4. The touch screen sensor ofclaim 1, wherein the optically continuous layer comprises an anti-glareor matte finish.
 5. The touch screen sensor of claim 1, wherein themicropattern comprises pseudo-random variations in the micropattern. 6.The touch screen sensor of claim 1, wherein the microscopic featurecomprises an anti-glare surface.
 7. The touch screen sensor of claim 1,wherein the microscopic feature comprises light-diffracting bumps. 8.The touch screen sensor of claim 1, wherein the microscopic featurecomprises light-diffracting pseudo-random or random surface structures.9. The touch screen sensor of claim 1, wherein the microscopic featurecomprises light-diffracting facets.